add function for handling action links

[andrecedik]

What has changed?

• users can now jump from the plugins page directly into the plugin settings

Please read the commit messages for details.

Things to review

• Link in plugin settings is shown and redirects to the shipcloud settings in WooCommerce

Common things:

• [x] Works fine.
• [x] Changelog written or not needed.
• [x] No conflict with current branch.

[andrecedik]

Since @ScreamingDev approved this PR in #165, I'm going to merge it now