Support github cache

[DiamonDinoia]

Dear @aminya,

Thank you for providing this action. It is really helpful to me.

I would like to ask if there is any technical reason why github cache cannot be leveraged somehow to avoid re-installing the same packages every time. My pipelines run the same env for multiple jobs and sometimes setup-cpp is the step that takes most of the time (example: https://github.com/DiamonDinoia/finufft/actions/runs/13046204138/job/36416878122). Is it possible to cache the installations, or the resulting image entirely to avoid doing the same work all the time?

Thanks,
Marco

edit: if you can help me setting up custom docker images. I am happy to contribute to the documentation

[aminya]

setup-cpp uses the cache where possible (e.g. apt packages are already installed, or brew package is already installed), but there's still room for improvement.

If you're using Linux, you can use the published docker images:
https://hub.docker.com/u/aminya
https://github.com/aminya/setup-cpp#prebuilt-docker-images

You can create your own images if you have a different setup:
https://github.com/aminya/setup-cpp#inside-docker

There are a lot of examples here:
https://github.com/aminya/setup-cpp/tree/master/dev/docker