Generating new Chroma syntax highlights

Chroma is the syntax highlighter used by Hugo, the static site generator that powers Materialize's docs. We have upstreamed a Materialize lexer (which is a slightly-modified version of their Postgres lexer). When new keywords are added we should upstream an update.

Generating a new lexer definition

Fork the Chroma repo and clone it locally as a sibling of the materialize repo.
From the root directory of the materialize repo, run the generate script:
```
./bin/gen-chroma-syntax
```
In the Chroma repo, commit the changes to the Materialize dialect file and submit them as a PR.