Basic RST -> Markdown

[gatesn]

Fixes #291

[lgeiger]

Thanks @gatesn for getting this started. This is a huge improvement 💯

[lgeiger]

According to the spec the this should be 'kind': lsp.MarkupKind.Markdown instead of 'type': lsp.MarkupKind.Markdown since hover requests return a MarkupContent object:

export interface MarkupContent {
	/**
	 * The type of the Markup
	 */
	kind: MarkupKind;

	/**
	 * The content itself
	 */
	value: string;
}

[gatesn]

And that’ll be why I’ve seen no marked improvement in VSCode!! Thanks for pointing that out.

I also note that docutils exists in Python, so we might want to make use of its RST parser instead of replicating the jacket typescript one in the VSCode plugin.