Provide maven-metadata.xml within Maven repo for Mend Renovate to work.

New Feature

Right now Mend Renovate attempts to fetch maven metadata from standard maven coordinates https://api.mapbox.com/downloads/v2/releases/maven/com/mapbox/maps/maven-metadata.xml to populate the list of versions. Unfortunately, this file is not available (curl -u mapbox https://api.mapbox.com/downloads/v2/releases/maven/com/mapbox/maps/android/maven-metadata.xml returns 404), so Renovate fails to generate the list of versions and decide if the update is required. Using the same credentials it's possible to fetch the actual artifact (example: curl -u mapbox https://api.mapbox.com/downloads/v2/releases/maven/com/mapbox/maps/android/11.4.0/android-11.4.0.aar), so the token we're using is valid and uses the proper DOWNLOAD:READ permissions.

Providing the valid maven-metadata will allow to utilize Renovate (or other similar tool like dependabot) and ensure timely updates.

Why

Mend Renovate eases the pain of maintaining up-to-date library set in our apps, and Mapbox usually evolves pretty fast, so we want to be on the latest version possible without spending extra efforts on the release monitoring.

Start with the Maven coordinates and curl requests in the issue, comparing the missing maven-metadata.xml response with the accessible android-11.4.0.aar artifact. Done means valid metadata is available at the documented Maven path so Renovate or a similar dependency tool can enumerate versions using the existing credentials.