Implement JS flipper client

Summary:
Standardize WS implementation for JS environments.

Why do we need a separate server implementation for browsers?
Browser targets cannot authenticate via the default certificate exchange flow. We need a dedicated client for them that works over an insecure channel (without the cert exchange).

Major changes:
1. Renamed `flipper-js-client-sdk` to `js-flipper` for consistency with `react-native-flipper`
2. Updated `js-flipper` implementation to match our other existing clients

Documentation will be updated in a separate subsequent PR.

https://fb.quip.com/2mboA0xbgoxl

Reviewed By: mweststrate

Differential Revision: D31688105

fbshipit-source-id: 418aa80e0fd86361c089cf54b0d44a8b4f748efa

js/js-flipper/tsconfig.json

@@ -0,0 +1,25 @@
+{
+  "compilerOptions": {
+    "outDir": "lib",
+    "esModuleInterop": true,
+    "target": "ES5",
+    "removeComments": true,
+    "preserveConstEnums": true,
+    "sourceMap": true,
+    "declaration": true,
+    "moduleResolution": "node",
+    "skipLibCheck": true,
+    "strict": true,
+    "strictFunctionTypes": false,
+    "downlevelIteration": true,
+    "module": "commonjs",
+    "baseUrl": "."
+  },
+  "include": [
+    "src"
+  ],
+  "exclude": [
+    "node_modules",
+    "**/__tests__/*"
+  ]
+}