revamp UI + show oncall/group

Summary:
Redesigns the bug reporting dialog:
- show information from `package.json`'s `bugs` field, where we can link to support groups or name oncalls.
- adds show/hide animation
- uses new button style

Reviewed By: jknoxville

Differential Revision: D13417287

fbshipit-source-id: 2948794e9b1f42bbd895981d5e4b0578a9b8ee2e

src/__tests__/__snapshots__/App.electron.js.snap

@@ -5,7 +5,7 @@ exports[`Empty app state matches snapshot 1`] = `
   className="css-1si6n3e"
 >
   <div
-    className="toolbar css-1u64wvw"
+    className="toolbar css-1cn9bxd"
   >
     <div
       className="css-q7gju5"