Summary

Adding in @-ms-viewport and @-o-viewport to the CSS grammar

Motivation

Because it currently breaks syntax highlighting if you use these selectors in my editor (VSCode), and I'm sure others using this grammar too.

I am aware that it is a deprecated selector. The main reason for still including it in ones code is being backwards compatible with IE etc. I would say, though I'm far from an expert on the viewport area

Describe alternatives you've considered

I don't see many other alternatives than living with broken syntax highlighting, or not including these tags, but as I see it there isn't a possibility that gets you both syntax highlighting and the backwards compatibility with old browsers utilizing these features. If there is I'd be happy to hear about it!

Additional context