.lagda.md support

[jonaprieto]

I was wondering if you could please support markdown files,
I would like to take advantage of the previewer for images and other stuff
of markdown. What I have now is files (.lagda) with markdown syntax inside except for
the agda blocks. (\begin{code}\end{code}).

[banacorn]

atom/atom#17551 is working on mixing different grammars in a single file.

So far as I'm aware of there are 3 kinds of markup languages Agda supports:

agda-mode/src/type.ts

Lines 8 to 13 in dec2fb3

	const enum FileType {
	Agda,
	LiterateTeX,
	LiterateReStructuredText,
	LiterateMarkdown
	}

[jonaprieto]

I see