Add a button to copy request path

**Link to problem area**: https://spec.matrix.org/

**Issue**
Have a button to copy the request path without needing to select it and ctrl+c

Something like this for example:

Start at the request-path display on https://spec.matrix.org/ and inspect how that page presents the path. Add a button that copies the request path without manual selection, then verify that the copied value matches the displayed path.

Written by the indexing model from the issue text.