Support visual studio code's preview scripts

[domoritz]

See https://github.com/mjbvz/vscode-markdown-mermaid for an example

[amitkaps]

Thanks @domoritz for asking for this. As @kachkaev mentioned now in #7 , markdown-preview-enhanced is already supporting vega-lite and vega in YAML as both atom and vscode extension. And also mermaid and much more...

So will focus on other stuff right now like inline execution --- check out the latest view on visdown.com and let me know what you think.