[Issue 18879] !is doesn't highlight correctly

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18879

--- Comment #7 from Rainer Schuetze <r.sagitario at gmx.de> ---
> Added distinct colour, or fixes for !is/!in? :)

"in" and "is" use color "Visual D Operator" if used as operators, and color
"Visual D Keyword" elsewhere.

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