* added support for markdown fenced math blocks
* original markdownEngine.ts
* Add fenced math block rendering to markdown-math
* Update dependencies
* custom parser for fenced math blocks
* custom parser for fenced math blocks
* reverted changes to extension.ts
* reverted all changes from prior implementations
* proper fence grammar implementation for math
---------
Co-authored-by: Matt Bierner <matb@microsoft.com>
aaronchucarroll