Add C3 language UDL

[gabrielezed]

No description provided.

[pryrt]

There are major problems with your submission:

1. You didn't include the JSON file update, which is part of the requirements for submission
2. You didn't follow the file naming scheme
3. The UDL was the old (pre Notepad++ 6.3, so from before Feb 2013) -- but even for that ancient, out-of-date version, it was invalid syntax.
4. Some of the Operator characters were interfering with the other syntaxes (folding, delimiters, and the prefix $ and @ keywords), so not everything was working

I am doing my best to fix it. But if the results aren't as you desire, then I'd suggest re-creating it in a modern Notepad++ (like v8.9.3), and doing the export from there, and submitting a new PR.