Feature Request: use .bonsai.yml file from github release assets instead of from the repository checkout.

[jspaleta]

Make it possible to read .bonsai.yml from github release assets instead of the tagged source code.

Releases without a .bonsai.yml file as part of its release assets would be silently ignored.
In fact, just remove the requirement for .bonsai.yml to have to exist in the default branch entirely and only require it to appear in releases as a release asset.

Benefits

1. This would make it possible to have test releases in github that do not get compiled publicly in bonsai.
2. makes it possible for CI/CD to validate/generate .bonsai.yml after release assets are built. Right now its .bonsai.yml has to be declared before binary assets are built, which is a bit backwards...