Support C# specific files(.props, .targets, .csproj, .sln)

[HavenDV]

Hello. Do you mind if I add support for these files as PR? Everything except .sln files is xml.
The .sln file provides its own format and can be opened as a regular text file. But we can also exclude this, this has the lowest priority.

[chamburr]

Please do! Let me know if you need any help.