Add config argument to specify valid markdown flavors (#1424)

* Try and add in support for quarto wikilink autocomplete as in https://github.com/MilesMcBain/foam

* Try and add in support for quarto wikilink autocomplete as in https://github.com/MilesMcBain/foam but make it general based on a new config in settings.json, "foam.supportedLanguages". That should allow for rmarkdown files as well.

* remove package-lock.json in favor of yarn.lock

Author: n8layman