add github action for releasing to snapcraft

[r0zbot]

TODO

• We still need to add the snapcraft token
• Deal better with x.y.z-something releases

[debdutdeb]

@r0zbot do we have RELEASE_IMAGES_ROCKETCHAT_WEBHOOK already? Maybe when you initially worked on this?

[r0zbot]

@r0zbot do we have RELEASE_IMAGES_ROCKETCHAT_WEBHOOK already? Maybe when you initially worked on this?

no, we have to add that with the snap credentials to this repo. I have the webhook handy, I'll add that, but can you get the creds?

[debdutdeb]

Yup! Thanks!