Add repository information to metadata endpoints

[halfbyte]

Our clients have asked us numerous times to support JSR for the npm-ish package managers we support - The main holdup was that we weren't supporting aliased packages (@std/http@npm:@jsr/std__http@^1.0.12 etc.) which we've now implemented. While testing, I realised that currently the npm compat metadata endpoint does not return a "repository" field as npm normally does.

We're using this URL to then gather more information about a package and specifically to find a CHANGELOG file or find out if GitHub releases are used to document changes.

This information is clearly available in the JSR database, as it is displayed on the website, so can we please add this to the metadata in the API as well? This is also missing from the native JSR metadata endpoint.