Fix broken links inside app

Summary:
Searched for broken link patterns inside the app itself. I think I found them all but it's not certain.

Patterns searched for and replaced:
```
.html
getting-started/)
getting-started)
getting-started"
```

and also searched the repo for regex `\]\(.*)` and checked them by eye.

Reviewed By: passy

Differential Revision: D21306944

fbshipit-source-id: a2e09b0fd8677f5f26e5cc4a06805b474247f7e6

desktop/app/src/MenuBar.tsx

@@ -365,15 +365,15 @@ function getTemplate(
         {
           label: 'Getting started',
           click: function () {
-            shell.openExternal('https://fbflipper.com/docs/getting-started/');
+            shell.openExternal(
+              'https://fbflipper.com/docs/getting-started/index',
+            );
           },
         },
         {
           label: 'Create plugins',
           click: function () {
-            shell.openExternal(
-              'https://fbflipper.com/docs/tutorial/intro.html',
-            );
+            shell.openExternal('https://fbflipper.com/docs/tutorial/intro');
           },
         },
         {

desktop/app/src/chrome/WelcomeScreen.tsx

@@ -138,9 +138,7 @@ export default class WelcomeScreen extends PureComponent<Props, State> {
           <Item
             onClick={() =>
               shell &&
-              shell.openExternal(
-                'https://fbflipper.com/docs/features/index.html',
-              )
+              shell.openExternal('https://fbflipper.com/docs/features/index')
             }>
             <Icon size={20} name="rocket" color={brandColors.Flipper} />
             <FlexColumn>
@@ -153,9 +151,7 @@ export default class WelcomeScreen extends PureComponent<Props, State> {
           <Item
             onClick={() =>
               shell &&
-              shell.openExternal(
-                'https://fbflipper.com/docs/tutorial/intro.html',
-              )
+              shell.openExternal('https://fbflipper.com/docs/tutorial/intro')
             }>
             <Icon size={20} name="magic-wand" color={brandColors.Flipper} />
             <FlexColumn>
@@ -166,7 +162,9 @@ export default class WelcomeScreen extends PureComponent<Props, State> {
           <Item
             onClick={() =>
               shell &&
-              shell.openExternal('https://fbflipper.com/docs/getting-started/')
+              shell.openExternal(
+                'https://fbflipper.com/docs/getting-started/index',
+              )
             }>
             <Icon size={20} name="tools" color={brandColors.Flipper} />
             <FlexColumn>

desktop/app/src/chrome/plugin-manager/PluginDebugger.tsx

@@ -218,7 +218,7 @@ class PluginDebugger extends Component<Props> {
           emulator/simulator currently running on your system, or is there a
           development device connected via USB? There are some devices/emulators
           known to have problems connecting to Flipper. Check out the{' '}
-          <Link href="https://fbflipper.com/docs/troubleshooting.html#known-incompatibilities">
+          <Link href="https://fbflipper.com/docs/troubleshooting#known-incompatibilities">
             known incompatibilities
           </Link>
           .
@@ -249,7 +249,7 @@ class PluginDebugger extends Component<Props> {
           <InfoText>
             To debug why Flipper couldn't establish a connection to the app,
             check out our documentation about{' '}
-            <Link href="https://fbflipper.com/docs/troubleshooting.html#connection-issues">
+            <Link href="https://fbflipper.com/docs/troubleshooting#connection-issues">
               connection issues
             </Link>
             .

desktop/pkg/src/commands/lint.ts

@@ -35,7 +35,7 @@ export default class Lint extends Command {
       const errors = await runLint(inputDirectory);
       if (errors) {
         this.error(
-          `Plugin package definition is invalid. See https://fbflipper.com/docs/extending/js-setup.html#plugin-definition for details.\n${errors.join(
+          `Plugin package definition is invalid. See https://fbflipper.com/docs/extending/js-setup#plugin-definition for details.\n${errors.join(
             '\n',
           )}`,
         );

desktop/plugins/rn-tic-tac-toe/index.tsx

@@ -124,9 +124,7 @@ export default class ReactNativeTicTacToe extends FlipperPlugin<
           <Info type="info">
             This plugin demonstrates how to create pure JavaScript Flipper
             plugins for React Native. Find out how to create a similar plugin at{' '}
-            <a
-              href="https://fbflipper.com/docs/tutorial/intro.html"
-              target="blank">
+            <a href="https://fbflipper.com/docs/tutorial/intro" target="blank">
               fbflipper.com
             </a>
             .

react-native/react-native-flipper/README.md

@@ -15,11 +15,11 @@ Note that this package requires React Native 0.62 or higher.
 ## Usage
 
 How to build Flipper plugins is explained in the flipper documentation:
-[Creating a Flipper plugin](https://fbflipper.com/docs/extending/index.html).
+[Creating a Flipper plugin](https://fbflipper.com/docs/extending/index).
 Building a Flipper plugin involves building a plugin for the Desktop app, and a plugin that runs on a Device (Native Android, Native IOS or React Native). This package is only needed for the plugin that runs on the mobile device, in React Native, and wants to use the JavaScript bridge.
 
 This package exposes one method: `addPlugin`.
-The `addPlugin` accepts a `plugin` parameter, that registers a client plugin and will fire the relevant callbacks if the corresponding desktop plugin is selected in the Flipper Desktop. The full plugin API is documented [here](https://fbflipper.com/docs/extending/create-plugin.html).
+The `addPlugin` accepts a `plugin` parameter, that registers a client plugin and will fire the relevant callbacks if the corresponding desktop plugin is selected in the Flipper Desktop. The full plugin API is documented [here](https://fbflipper.com/docs/extending/create-plugin).
 
 ## Example