Plugin Repository maintenance approach

[melonamin]

As of now Plugin Repository feature of SwiftBar relies on repository.json. The content is derived from bitbar-plugins.

Some thoughts on a possible target state:

• bitbar-plugins is pretty active, there is no reason to entice people to move their plugin to this repository unless it uses SwiftBar specific features
• repository.json definition file should be edited though PRs, one PR for one plugin change

TODOs:

• Create a PR template for repository.json changes
• Create a PR template for plugin changes, if plugin is stored in this repository
• Build GitHub Action to populate repository.json from bitbar-plugins. Action should open a PR request, human approval required
• make it clear repository.json what is the source of the plugin like repository=bitbar-plugins or something like that. Make sure that UI shows it explicitly.