C# Arrow functions with string breaking color themes

[alexdima]

Moved from microsoft/vscode#10645

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From @mnsr

VS Code: 1.4.0

This issue is similar to this one for TS: microsoft/vscode#3919

But in this case, it's happening in C# after using an arrow function AND the new string format syntax:

protected string Name(string name) => $"My Name is {name}";

if you remove the curly braces from the string, it's fine:

protected string Name(string name) => $"My Name is name";

[ivanz]

This is duplicate of #638 and I have just opened a pull request a moment ago to fix it in #681 :)