feat: add `--clear-cache` option

[patricedenis]

This PR is about adding an option to clear the local caches. It is supposed to delete the files that store the tldr pages locally on your computer. I was inspired by the same option that already exists on the tldr-node-client.

It may resolve #242 has after application, no local cache should remain on the storage. Also I'm not sure that the workflow automates the build of the man page (this is not modified in current PR). If not, I could try to modify the building workflow to allow that.

I would again be very pleased if someone could test this PR locally before merging if wanted because I haven't set a development environment yet.