Github action for "nightly" builds of the bindings

[Nereuxofficial]

I made a short workflow that checks out the newest Flipper Zero Mainline firmware, builds bindings against it and pushes it into a "nightly" branch.

This is more of a proposal. Using this would allow:

• Users to use bindings built against the git version of the flipper zeros firmware via:

  [dependencies]
  flipperzero = { git="https://github.com/flipperzero-rs/flipperzero", package="flipperzero", branch="nightly"}
  flipperzero-sys = { git="https://github.com/flipperzero-rs/flipperzero", package="sys", branch="nightly" }
  flipperzero-rt = { git="https://github.com/flipperzero-rs/flipperzero", package="sys", branch="nightly" }
  flipperzero-alloc = { git="https://github.com/flipperzero-rs/flipperzero", package="sys", branch="nightly" }

  And they could also specify a specific commit to pin the dependency.

• Early discovery of API-changes to bindings
• Fully automatic builds against the newest SDK potentially also useable for custom firmware or at least easier to adjust to custom firmware

[dcoles]

At present we're using the Dockerfile in tools to generate bindings in a relatively reproducible way.

I need to think a little more about the implications of creating a "nightly" branch like this (it's really flipper-firmware@dev nightly), especially if folks are going to start depending upon it.

Perhaps a better approach would be to generate a binary artefact that can be easily downloaded, a bit like what is done on updates.flipperzero.one. Though I do feel that moving away from checking-in the bindings is going to be the better option long-term, so folks aren't pinned to a specific SDK.