feat: support github discussions

[bjohansebas]

With this, GitHub discussions can now be added to the agenda, since there may be discussions that should be included in the agenda.

There is no REST API to retrieve repository discussions; this is done through GitHub's GraphQL API: https://docs.github.com/en/graphql/guides/using-the-graphql-api-for-discussions

See how it works (bjohansebas#41).

[ctcpip]

🎉 neat!

a couple things:

1. needs error handling
   • while there is a large try/catch for the surrounding code, we would not want the entire operation to fail if there was only a failure in this code for retrieving discussions
2. would like to see an option for this
   • not sure if this would be better as an opt-in or an opt-out, but it should be configurable
3. needs test(s)

[bjohansebas]

@wesleytodd Could you please enable discussions in the repository?