third-party-licenses: add syntect_server licenses

Created by: slimsag

This PR adds third-party licenses for syntect_server. I did not use CSV format and used multiple files because documenting/explaining all of this is a little bit cumbersome to do.

The dependencies.json is auto-generated via a script while the syntaxes.txt is hand-crafted and will have to be maintained as part of adding any new language syntaxes: https://github.com/slimsag/Packages#license

Note: This information is only up-to-date for Sourcegraph >= v3.21, since that version of Sourcegraph removes some syntaxes which had missing/incompatible licenses

Fixes #11269