Add support for YARA syntax

[redteampanda-ng]

This is my first lexer I tried my hands on. Since we are dealing with a lot of YARA syntax in our technical documentation, I wanted to write a lexer for this. Please let me know if there is potential (most likely) to improve the regex.
Also had to remove the number and hex regex, since they caused some problems.

Thank you

[jeanas]

A few more comments, should be good to go afterwards.

[jeanas]

LGTM, but please have a look at the CI failures. Basically, you need to rerun tox -e mapfiles and tox -- --update-goldens.

[redteampanda-ng]

Should be working now

[jeanas]

Thanks!