Add Support for C# XML documentation highlight

[digitsisyph]

Describe what you want

Currently, C# XML documentation would be treated as plain comments and not be highlighted.

Current bahavior:

Desired behavior:

Additional context

This can be easily achieved by adding following rules:

"[One Dark Pro]": {
        "textMateRules": [
            {
                    "scope": "comment.documentation",
                    "settings": {
                        "foreground": "#608B4E",
                    }
                },
                {
                    "scope": "comment.documentation.attribute",
                    "settings": {
                        "foreground": "#C8C8C8",
                    }
                },
                {
                    "scope": "comment.documentation.cdata",
                    "settings": {
                        "foreground": "#E9D585",
                    }
                },
                {
                    "scope": "comment.documentation.delimiter",
                    "settings": {
                        "foreground": "#808080",
                    }
                },
                {
                    "scope": "comment.documentation.name",
                    "settings": {
                        "foreground": "#569CD6",
                    }
                },
      ]
    }

Reference: https://github.com/OmniSharp/omnisharp-vscode/issues/3816

[Binaryify]

could you provide some test code

[e-potashkin]

Example from One Dark Pro in JetBrains Rider

[Binaryify]

it's look like this now

[digitsisyph]

It looks it has been done. Thank you!