The highlighting isn't an issue, I think most editors cheat in the same way. As C++ is a super-set of C it shouldn't be a problem, at least not except for a few edge cases which I wouldn't worry about IMHO.
My comment was more that the C example code is actually C++.
Well MSVC only just supports C99 so asking for C11 keywords is unlikely to happen.
I had a quick look at their C++ word list [0] and it looks like _Imaginary and _Complex and _Bool are the only missing C99 keywords. Feel free to make a PR if you want them added :)
restrict is C99. Many C++ compilers accept __restrict__ or some other form of it to mean the same, but restrict doesn't exist in the C++ standard, so the GP is correct.
My comment was more that the C example code is actually C++.