This PR is the last part of a series of changes to address various markdown syntax violations.
I ported the ReposProvider readme template infra from dotnet-docker to eliminate duplication that would otherwise exist with these changes.
I discovered we were referencing a dead link to a dotnet-nightly product family repo that doesn't exist. I removed the dotnet-nightly related repos section of the readmes
To be consistent with dotnet-docker I added the product family to the related repos section of the readmes.
Related to https://github.com/dotnet/dotnet-docker/issues/5316
This PR is the last part of a series of changes to address various markdown syntax violations.