router-href custom attribute is hard to find

I haven't been able to find the `router-href` custom attribute in the documentation.

I think this should be in the Routing section, maybe a new subsection called "Binding".

In Addition, it could be in the "Bindings" and "Cheatsheet" sections.

Search the documentation for the Routing, Bindings, and Cheatsheet sections, then check where custom attributes are currently described. Document the `router-href` custom attribute in the most appropriate location, considering the proposed Routing "Binding" subsection and cross-references to the other sections.

Written by the indexing model from the issue text.