Add support for certain files from .NET ecosystem

- Visual Studio solution file, .sln
- .NET project files: .csproj, .fsproj, .vbproj
- F# script files, .fsx
- MSBuild files, .props (such as Directory.Build.props)

src/reuse/comment.py

@@ -604,6 +604,7 @@ class XQueryCommentStyle(CommentStyle):
     ".cs": CCommentStyle,
     ".csl": HtmlCommentStyle,  # Bibliography (XML based)
     ".css": CssCommentStyle,
+    ".csproj": HtmlCommentStyle,
     ".csv": UncommentableCommentStyle,
     ".cu": CCommentStyle,
     ".cuh": CCommentStyle,
@@ -621,6 +622,7 @@ class XQueryCommentStyle(CommentStyle):
     ".ex": PythonCommentStyle,
     ".exs": PythonCommentStyle,
     ".f": FortranCommentStyle,
+    ".fsproj": HtmlCommentStyle,
     ".f03": ModernFortranCommentStyle,
     ".f08": ModernFortranCommentStyle,
     ".f90": ModernFortranCommentStyle,
@@ -634,6 +636,7 @@ class XQueryCommentStyle(CommentStyle):
     ".ftn": FortranCommentStyle,
     ".fpp": FortranCommentStyle,
     ".fs": CCommentStyle,
+    ".fsx": CCommentStyle,
     ".ftl": FtlCommentStyle,
     ".gemspec": PythonCommentStyle,
     ".go": CCommentStyle,
@@ -716,6 +719,7 @@ class XQueryCommentStyle(CommentStyle):
     ".pptx": UncommentableCommentStyle,
     ".pri": PythonCommentStyle,
     ".pro": PythonCommentStyle,
+    ".props": HtmlCommentStyle,  # MSBuild files
     ".proto": CCommentStyle,
     ".ps1": PythonCommentStyle,  # TODO: Multiline comments
     ".psm1": PythonCommentStyle,  # TODO: Multiline comments
@@ -754,6 +758,8 @@ class XQueryCommentStyle(CommentStyle):
     ".scsyndef": UncommentableCommentStyle,
     ".sh": PythonCommentStyle,
     ".sld": LispCommentStyle,  # Scheme Library Definition (R7RS)
+    # Visual Studio solution file, officially uncommentable:
+    ".sln": UncommentableCommentStyle,
     ".sls": LispCommentStyle,  # Scheme Library Source (R6RS)
     ".sml": MlCommentStyle,
     ".soy": CCommentStyle,
@@ -778,6 +784,7 @@ class XQueryCommentStyle(CommentStyle):
     ".ui": HtmlCommentStyle,
     ".v": CCommentStyle,  # V-Lang source code
     ".vala": CCommentStyle,
+    ".vbproj": HtmlCommentStyle,
     ".vim": VimCommentStyle,
     ".vm": VelocityCommentStyle,
     ".vsh": CCommentStyle,  # V-Lang script