Consider adding support for dependency caching

[ross-paypay]

First: Thanks for this action, its very helpful.

It would be super awesome if this action could add support for caching dependencies so that builds do not need to redownload and recompile them. I think maybe we could take some inspiration from the Rust Cache action.

Or maybe this cache could be used with the Rust Cache action together? 🤔

[Douile]

With how we currently work (building in a Docker container in /rust/build) other actions steps can't access the build files.

This would be possible in the future if:

• we build in the /github/workspace directory: https://docs.github.com/en/actions/creating-actions/creating-a-docker-container-action#accessing-files-created-by-a-container-action
• used a composite action instead of docker (Add more support for targets #4)