js api improvements: responnders, communication protocol

Summary:
A few improvements to JS API:
1) non-dummy responders - now we can reply to flipper
2) respecting flipper communication protocol: getPlugins, getBackgroundplugins, init, deinit, execute

adding linters

Reviewed By: jknoxville

Differential Revision: D22307525

fbshipit-source-id: 2f629210f398d118cc0cb99097c9d473bb466e57

flipper-js-client-sdk/src/example.ts

@@ -7,10 +7,19 @@
  * @format
  */
 
-import {FlipperClient, AbstractFlipperPlugin} from './api';
+import {FlipperClient, FlipperConnection, FlipperPlugin} from './api';
 import {newWebviewClient} from './webviewImpl';
 
-class SeaMammalPlugin extends AbstractFlipperPlugin {
+export class SeaMammalPlugin implements FlipperPlugin {
+  protected connection: FlipperConnection | null | undefined;
+
+  onConnect(connection: FlipperConnection): void {
+    this.connection = connection;
+  }
+  onDisconnect(): void {
+    this.connection = null;
+  }
+
   getId(): string {
     return 'sea-mammals';
   }
@@ -19,10 +28,9 @@ class SeaMammalPlugin extends AbstractFlipperPlugin {
     return true;
   }
 
-  newRow(row: {id: string, url: string, title: string}) {
-    this.connection?.send("newRow", row)
-}
-
+  newRow(row: {id: string; url: string; title: string}) {
+    this.connection?.send('newRow', row);
+  }
 }
 
 class FlipperManager {