expose forward lookup via inner cdn url

[tripodsan]

Is your feature request related to a problem? Please describe.
the content proxy will have a lookup feature, that redirects a inner cdn path to a onedrive or gdrive document.
see adobe/helix-content-proxy#212

instead of invoking the content proxy directly, this could be done through the inner cnd, eg:

• https://theblog--adobe.hlx.page/en/index.edit

would internally invoke the content proxy with:

https://adobeioruntime.net/api/v1/web/helix/helix-services/content-proxy@v1?owner=adobe&repo=theblog&ref=master&lookup=/en/index

which will calculate the respective document link and send a redirect to it.