Amending Base10 to slightly darker `#202122` to fulfill WCAG
requirements in connection to Accent50.
Also sligthly adapting hover derivative to `#404244` and amending
corresponding opacity hover value.
Bug: T248393
Change-Id: Id72829d837d9e8d37bbec6092e5055f7c182db7a
A resources folder is the defacto-standard across mediawiki repos.
Vector now mirrors those by describing where files served by ResourceLoader
are located.
Change-Id: Ib7d8575112e8afaaa84221a6f30a15b34b51eb24