web: highlight search operators and/or/not

Created by: rvantonder

Adds highlighting for and/or/not. It does not have to be these colors. @rrhyne @felixfbecker please weigh in your thoughts on a color choice for operators and I will update it. I picked the dark mode purple-ish color based on the VScode rendering of the return keyword in vscode, (which I think uses our theme?). For light mode I just picked something reasonably close.

Here is what it currently looks like:

Since I didn't find tests that would specifically break the color highlighting, I didn't add any for that. Though, I'll add some tests to make sure we lex the right ranges for these operators I did some exhaustive manual testing, and also updated our existing tests that already have test inputs for parsing operators.