add go scaffolding to #19479
Created by: ggilmore
Add-on to https://github.com/sourcegraph/sourcegraph/pull/19479
This PR:
- adds logic to read a manifest file containing the current name of the app bundle, and load it into a go struct
- modifies the app.html template to read the current name of the app bundle file
- modifies the watchman config to reload the frontend binary if either the manifest file or app.html file are modified
- adds a "shim" manifest that contains the current name of the app.bundle.js file (placeholder until the webpack logic is wired up)