Show GitHub downloads as badge with link to detailed report

[dbast]

This helps the see the overall download numbers and the popularity of all the variants.

Also updating the exiting build status badge to the new GitHub URL format that uses the yaml workflow filename instead of the workflow name.

Checklist

• [ ] Used a personal fork of the feedstock to propose changes
• [ ] Bumped the build number (if the version is unchanged)
• [ ] Reset the build number to 0 (if the version changed)
• [ ] Re-rendered with the latest conda-smithy (Use the phrase code>@<space/conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• [ ] Ensured the license file is being packaged.

[hmaarrfk]

thanks