Recommend source-build compatible dependabot pattern

[MichaelSimons]

Some .NET repos (e.g. templating and msbuild) have taken a dependency on utilizing dependabot to update dependencies. The standard pattern is not compatible w/source-build because the dependent package versions gets hard-coded and not overridable by source-build.

Investigation should be done to see if version properties can be utilized that source-build can override. Regardless on the finding repo follow-up needs to be done to update/recommend against the existing patterns being used. Source-build documentation should also be created that captures the recommendation.

[rainersigwald]

@jeffkl you worked with dependabot folks to get the central package version pattern supported, right? Do you have contacts that could help with this?

[jeffkl]

Unfortunately no, they never contacted me and implemented it entirely on their own.

dependabot/dependabot-core#1311

It would be cool to extend dependabot to know about more files with the configuration, I don't see an existing issue for that.

Existing list of files it searches:

https://github.com/dependabot/dependabot-core/blob/8315e7b213870959158c1c2bcfb482728a7e801a/nuget/lib/dependabot/nuget/file_fetcher.rb#L117

And items it looks for:
https://github.com/dependabot/dependabot-core/blob/8315e7b213870959158c1c2bcfb482728a7e801a/nuget/lib/dependabot/nuget/file_parser/project_file_parser.rb#L17-L21