Enable GitHub Discussions.

[RokeJulianLockhart]

Is your feature request related to a problem? Please describe.
I'd like to be able to ask questions, like whether this requires a bridge.

Describe the solution you'd like
Enable https://github.com/github/docs/blob/3f4776ee823022ac5394ce61e3f53b72c46d6004/content/discussions/collaborating-with-your-community-using-discussions/about-discussions.md#about--data-variablesproductprodname_discussions-.

Describe alternatives you've considered
Add a third preset to https://github.com/clemenskoprolin/light-party/issues/new/choose (and a label for it).

Additional context
8go/matrix-commander#68 (comment)