Cache dependencies using GitHub cache

[Marko19907]

It would be great if the workflow could cache dependencies using GitHub cache so you don't need to download them on every run. This would help speed up the build process and reduce the amount of time it takes to export a project.

An example of an implementation can be found in the actions/setup-node repository https://github.com/actions/setup-node

[moorbren]

Yeah it's pretty miserable using Tux Family to download every single build, think their getting hit with a ton of traffic and my builds are 7+ minutes, 95% of which is downloading the libraries. The export templates in Godot 4 are 800mb now, no light download for each build by any means. In some cases I was hitting build times of 20+ minutes.

In the meantime, I've downloaded the libraries and popped them into a local server for my runner. My builds now only spend a couple seconds downloading the files. Not super happy with it but speed wise it's pretty solid.

Here's a screenshot of some of the download times I was seeing:

[firebelley]

Addressed in #113