Enable token authentication

This PR adds token authentication flow to the extension.

Changes

Added login command.
- Internally it grabs pasted token and saves it in local fs.
- Having token means the user is authenticated which triggers policy puller which starts fetching policies (initially and periodically).
Added logout command.

I will work on README adjustments in separate PR (or add post-review) so we can review the code already.
Keep in mind that logic related to auth (mostly store.ts), api communication (mostly api.ts) and probably git related should/will be extracted to separate core package/s.
Maybe we can use build-in authentication interface, looks a bit complex for token authentication only but maybe for later 🤔 (see examples 1, 2).
I started to feel that code got a bit too closely tangled and some utils have too much knowledge/responsibility. It seems that we may need to go more into event-driven architecture or have something for better state management (or just clean it up, what I'm planning to do).