jsdoc to markdown functionality added

[pankaj2k9]

No description provided.

[digisomni]

This is for use in Docusaurus.

[ctrlaltdavid]

npm run generate-jsdoc-to-markdown
This converts HTML documentation into markdown in \docs\markdown
However, it isn't well formatted and includes a lot of Vue/Vuetify code which is rendered as text.

npm run markdown-docs
This runs typedoc on the code and generates markedown in \vircadia-dev-docs
The output includes private members etc. which is unwanted.
No text is included because all text is currently in Vircadia-specific JSDoc comments.
Global replace of /*@sdkdoc with /** creates better looking output, though it still includes private members.
Note: Lots of Docusaurus warnings/errors to fix up.