Add GitHub Actions workflow to clean up caches

[luisaveiro]

The "Setup Node" composite action enables caching on the actions/setup-node GitHub Actions. The actions/setup-node has built-in functionality for caching and restoring dependencies. It uses actions/cache GitHub Actions under the hood for caching global package data but requires fewer configuration settings.

Utilising caching in our GitHub Actions makes our workflows faster, and more efficient. This helps to reduce the billable time for GitHub Actions. However, we need to automate the process of managing GitHub Actions caches and automatically delete cache that is no longer needed (e.g. cache from merged pull requests).

According to GitHub documentation for force deleting cache entries.

Once a repository has reached its maximum cache storage, the cache eviction policy will create space by deleting the oldest caches in the repository. In order to prevent cache thrashing when this happens, you can set up workflows to delete caches on a faster cadence than the cache eviction policy will.

GitHub documentation includes an example workflow that uses gh-actions-cache to delete up to 100 caches created by a branch once a pull request is closed.