Rich text support

Support for inline text styling with BBcode style syntax:
* Italic using `[i] [/i]`
* Bold using `[b] [/b]`
* Underline `[u] [/u]`
* Strikethrough `[s] [/s]` 

As per: https://www.bbcode.org/reference.php

For the following:
- [ ] Canvas Renderer
- [ ] WebGL MSDF text renderer