Add lexer for PRQL

[vanillajonathan]

Adds a lexer for the PRQL query language.

PRQL is a modern language for transforming data — a simple, powerful, pipelined SQL replacement.
https://prql-lang.org/
https://github.com/PRQL/prql

[Anteru]

Hello! This needs a test file before we can continue, look at the contribution page.

[Anteru]

Thanks for updating the _mapping file etc., but please do add an example file as well under /examplefiles.

[Anteru]

Thanks for the updates! Before we do burn down a forest here running CI, can you make sure to run the checks locally? Is there anything preventing you from using tox? I need to manually approve the CI run, and it's fairly simple stuff to fix that can be all checked locally.

[vanillajonathan]

I can use tox but I am a bit new to this, I hadn't used it before.

[Anteru]

pip install tox (in the virtual environment you use for development) and then tox, tox -e check, and possibly tox -e mapfiles (to regenerate them)

[Anteru]

prql.py is missing the correct copyright info. It has to be 2006-2023, not just 2023.

[vanillajonathan]

@Anteru I've updated the copyright into.

[Anteru]

Merged, thanks!