integrate with briefcase to build distributions

[rfletchr]

Issue

there are not easily downloadable distributions available.

Proposal

• make a new repo called 'cocktail-dist'
• setup a skeleton briefcase application which requires cocktail
• add CI jobs to build for each platform

Considerations

• would it be better to just adopt briefcase fully and restructure the main repo?

[rfletchr]

having looked at briefcase it's trying to do far too much, and enforces a workflow I'm not interested in adopting.