add review comment to sb files

[oleksandr-didyk]

Contributes to dotnet/source-build#3435

Adds comments to source-build files asking for the inclusion of the source-build team in PRs that alter SourceBuild* files. Non-reviewed changes could potentially cause issues down the line, be it in the downstream repos or the product build (as has happened in the past, see dotnet/source-build#3435 (comment))

[333fred]

Rather than comments, please update the CODEOWNERS file to include the relevant files and the source build team, so that it automatically includes you on such PRs.

[oleksandr-didyk]

Rather than comments, please update the CODEOWNERS file to include the relevant files and the source build team, so that it automatically includes you on such PRs.

Initially wanted to add both the comment and the CODEOWNERS entry, but for a team to be added as a code owner it needs to have write permissions to the repo and I wanted to verify first if this is something we would need. I should've mentioned that in the description though, my bad, forgot to edit it.

If you are OK with granting write permissions to dotnet/source-build-internal, I will add the CODEOWNERS entry.

[oleksandr-didyk]

@333fred soft ping - would write access to the team be considered as an option or can we move on with merging this PR as is? Thank you!

[333fred]

@oleksandr-didyk write access for dotnet/source-build-internal has been added.

[oleksandr-didyk]

@oleksandr-didyk write access for dotnet/source-build-internal has been added.

Thank you!

Added the CODEOWNERS entry for source-build