Starmath syntax hightlight

The starmath syntax highlight first revision is now available here:
https://gerrit.libreoffice.org/c/core/+/109639/21

I write asking for a deep review since it's a patch that may change the
user experience.
I'd like the UX team to take a look and evaluate the code legibility.
Note that bright colors have been avoided.
Maybe some documentation should be added.
Get sure the preferences page keeps up to the accessibility and quality
standards.
Can get a stability test with some twisted starmath code I haven't thought
of.
I can't think of any automated test, but it may be possible.

Hi Dante!

Thank you for the initiative! Syntax highlighting is something I have
always wished to see in StarMath. I am myself a frequent user of StarMath,
so I can tell that this will be a great addition to the application.

The current Formula Editor does not provide a good experience, especially
when the formula gets very long. Also, it becomes hard to spot syntax
mistakes if there's no highlighting.

I'll pull and build your patch later today to see how it performs. Then
I'll try to provide some feedback from the user perspective. However, my
experience with the LibreOffice codebase is limited, so I can't help with
automated tests.

Regards,
Rafael Lima

Respective ticket is https://bugs.documentfoundation.org/show_bug.cgi?id=138129

The actual TDF is 43089
https://bugs.documentfoundation.org/show_bug.cgi?id=43089