Component importer should replace links to all imported files

Currently only links to component reference docs are converted to internal links on import.
But we also import some specific pages where the links are not changed.

We can use the import `spec.json` to map links to imported paths and rewrite matching links.

An example is the link `AMP.pushState()` here:
https://amp.dev/documentation/components/amp-bind/?format=websites#modifying-history-with-amp.pushstate()

Start by locating the import spec.json and the importer that converts component reference links. Use the AMP pushState() example to trace how links to specific imported pages are handled. Done means matching links to all imported paths are rewritten as internal links, not only component reference documentation links.

Written by the indexing model from the issue text.