Bundle the frontend as a web target

[bgrins]

If we want to load the browser chrome over http we will need to bundle it as a web app instead of an electron-renderer app.

This would also prevent from leaking node / electron dependencies into the frontend

[bgrins]

This will require introducing some externals in the webpack config, and we'll also need to use websockets instead of ipcRenderer for main process <-> renderer process communication

[mykmelez]

@bgrins had a WIP branch for this at one point: https://github.com/bgrins/tofino/tree/no-node