plugin support

[rsteube]

Add plugins bool (intended for root command) to enable implicit embedding of [spec.name]-plugin completion (e.g. cargo-fmt, git-extras).

name: example
plugins: true

[rsteube]

Or should this just be the default behaviour without config? Maybe have an external configuration for this.

[rsteube]

Additional specs using dot as delimiter might be a good way.

example.pluginA.yaml gh.dash.yaml

No specific config required and plugins are registered implicitly.