feat: publish a snap of stream sprout

[flexiondotorg]

I confirm this feature has not been previously requested

• I have searched the issues and this feature has not previously been requested

Is your feature request related to a problem? Please describe.
Make Steam Sprout more accessible to potential users by creating a snap.

Describe the solution you'd like
A snapcraft.yaml and CI to build/publish a snap.

Describe alternatives you've considered
A .deb is really and available, and a container image is in the works.

Additional context
Snappy, snap, snap! 🐊