Make it more obvious that the cache call does double duty

[axelson]

I wasted 20+ minutes because I didn't realize this and couldn't find the information in the documentation anywhere. Hopefully adding it to the Readme will help someone else avoid that pain in the future.

[ludwigschubert]

Same here, but I'd suggest a slight rewording of your note:

sets up a hook to restore the

should probably read sth like

sets up a hook to post (upload) the new version of the cache

I'm including "post" as it seems to be the terminology Github has chosen to use for this.

Thanks for opening a PR, though; I feel this is a simple but important improvement.

[vsvipul]

Our example at https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows should be good enough to make this obvious that the cache needs to be restored before the cached files are required.

Adding @lucascosti to take a look and if a change is required, we should probably add that to the above docs page.

[vsvipul]

Thank you @axelson and @lucascosti for adding this.