[FEATURE] Add mvBase PROC as a language option.

[TedCha]

Is your feature request related to a problem? Please describe. I work at company who uses a lot of PROCs within their menus and some of their processes. It's pretty annoying to have to edit these files because there is no syntax highlighting at all. I published my own mvBase PROC syntax highlighting extension to the marketplace but it would probably make more sense to be in this extension rather than as a standalone extension.

Currently everything works pretty well, there's a few known issues that I need to fix (user exits have not been accounted for and the T command could use some work). If you think it's a good idea for it to be a part of this extension, I'd be happy to submit a pull request once I fix the mentioned issues.

BTW, this project is awesome! It's so cool to see open source for mvBasic.