Fix most lint warnings

Summary:
I noticed that after the typescript upgrade, I got several weird positives from ESLint (like unused parameters in a type definition, which are obviously always unused, e.g. `type onClick = (e: Event) => void`). After some investigation, it turned out these warnings are generated by eslint, but that those rules should be performaned by typescript/eslint instead. For future reference to which rules this applies:

https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/README.md#extension-rules

Updated the config, and while at it, fixed all warnings in our codebase, except for `react-hooks/exhaustive-deps` warnings, since those require semantic changes.

This reduces the amount of eslint warnings from 86 to 39.

Reviewed By: passy

Differential Revision: D23905630

fbshipit-source-id: 0557708fd9ec6b17840a3c191e7d3baf225bdf23

desktop/plugins/crash_reporter/index.tsx

@@ -387,7 +387,7 @@ function addFileWatcherForiOSCrashLogs(
     // Directory doesn't exist
     return;
   }
-  fs.watch(dir, (eventType, filename) => {
+  fs.watch(dir, (_eventType, filename) => {
     // We just parse the crash logs with extension `.crash`
     const checkFileExtension = /.crash$/.exec(filename);
     if (!filename || !checkFileExtension) {
@@ -643,7 +643,7 @@ export default class CrashReporterPlugin extends FlipperDevicePlugin<
       const referenceDate = new Date();
       (function (
         store: Store,
-        date: Date,
+        _date: Date,
         setPersistedState: (
           pluginKey: string,
           newPluginState: Maybe<PersistedState>,