♻️ Refactors the src structure

[skellock]

The directory structure wasn't sitting right with me, so I've refactored it to become more like a single platform app.

I don't think I need to have a breakdown of main and renderer. That's something that the bundler can easily separate.

I'm not sure if people will get confused as to what belongs where, but I don't.

For example src/views/main-window and src/views/menu belong to the main processes, where as everything else under src/views is the renderer process.

I like this better. It feels less divisive.