[UX] Add Keyboard global shortcuts

[flavioislima]

This pull request adds several hotkeys to improve the user experience of our application. The new hotkeys are as follows:

CommandOrControl+R: Reloads the app
CommandOrControl+Q: Quits the app
CommandOrControl+Shift+I: Opens the dev tools
CommandOrControl+K: Opens the Heroic settings screen on the frontend
CommandOrControl+L: Opens the library screen
CommandOrControl+J: Opens the downloads screen

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Use the following Checklist if you have changed something on the Backend or Frontend:

• Tested the feature and it's working on a current and clean install.
• Tested the main App features and they are still working on a current and clean install. (Login, Install, Play, Uninstall, Move games, etc.)
• Created / Updated Tests (If necessary)
• Created / Updated documentation (If necessary)

[arielj]

Tested on linux and it works fine 👍

I have 2 questions but I don't think they are blockers:

• Maybe Ctrl+D can open the Downloads screen?
• I wonder if there's a way to add menu entries for the library, downloads, and settings shortcuts so then users can discover the shortcuts from the menu like you can discover things like quit/reload/devetools

Or maybe an idea for the future to show this information somewhere inside heroic.

[Nocccer]

LGTM. To avoid filling up main.ts again, is it possible to move the shortcuts to another file/folder?

[flavioislima]

@ariel, yes we need to make them more discoverable and we can expand that in the future. For now I think as a first implementation is fine though.