BBCode syntax highlighting

## Prerequisites
- [x] I have searched open and closed issues for duplicates.

## Feature
**Is your feature request related to a problem? Please describe.**

Syntax highlighting for BBCode, typically used on forums. E. g. `[b][/b]` for bold, `[url=https://google.com][/url]` for hyperlinks, etc.

**Describe the solution you'd like**

BBCode tags should be highlighted in different colours, as is possible for Markdown, HTML, freakin' COBOL, etc.

**Existing work**

BBCode highlighting packages exist for text editors like TextMate, Atom, and SublimeText; it can also easily be implemented in Notepad++.

**Describe alternatives you've considered**

- switching to a different text editor (I'd rather not)
- just gittin' gud (see above)

**Additional context**

I am like 90% sure more people use BBCode than COBOL.