match, sigh, cert, pem: Document better what files are generated, what is installed into Keychain

The codesigning stuff is still scary, especially if you can't "just" use `match`. It could help if the docs could give some additional information what files are created, what exactly is installed in the keychain etc when running the action.

Tasks here:

- Find out which actions are in this "area" additionally to the ones I mentioned above
- Look through the code of them and note down the files created etc.
- Update the documentation to e.g. have a table or something that lists the artifacts that are created and stored