feat: move to app folder on first run

[codebytere]

Closes #417.

When gitify first opens, it will now request to move itself to the Applications folder on macOS. The user's choice will be stored for subsequent runs. If it's already in the Applications folder, no prompts are shown.

cc @manosim I pulled the functionality into a new file but if you'd prefer I can put it into main.js or do something else entirely with it, up to you!

[manosim]

Looks great @codebytere 🎉

I think we will have to include first-run.js in electron-builder's configuration as currently, it won't be included when packaging (yarn make:macos). By the way, does this support/ignore Windows & Linux?

I agree with pulling that functionality to a separate file - one for the future - if we get more files like that, it might be worth pulling in a separate directory?

[codebytere]

@manosim yes - it skips if we're not on darwin. app.moveToApplicationsFolder is macOS-only but this is primarily in that other platforms are less opinionated about application location and/or handle it at the system level, so there's not really a cross-platform expectation for this type of user pattern there I wouldn't say.