Add ` source` tag to controller config

[Wolfy76700]

For the sake of completeness, we should add a source tag for controller specifications

e.g.: https://github.com/Wolfy76700/ControllerDatabase/blob/ec9ac5899f4e972f8fcc52d2a029f9e7eb04d394/pad/nintendo/gcn/config.json#L85

Ideally most of our sources should either come from The Internet Archive or be links to Wayback Machine archives.