syntax highlighting: improve comment contrast, add GraphQL highlighting
Created by: slimsag
This updates syntect_server for two changes:
- A change by @rrhyne to improve comment contrast (primarily in light theme): slimsag/syntect#7
- An awesome change by @rvantonder - adding his new open-source GraphQL syntax: slimsag/Packages#4
Helps #14546
Fixes #13935