Split stable notification into two steps

[Eeems]

• Stop using hub and instead use the github cli
• Create new draft release as part of stable build
• Split out discord notification to its own action that triggers on release. This means someone needs to go and publish the draft release

[Eeems]

I haven't tested this as there is no easy way in the current repo, and I don't have capacity to set up a standalone test repo for it right now.

I would appreciate someone else setting up a test repo though.