Support for GFM-like checkboxes

[chrisalley]

@tmpfs

@chrisalley, being new here I am not totally clear about extensions and how they work. Where can I find out more on extensions to Commonmark? Are they part of a separate specification Commonmark Extensions and then implementations can enable/disable these extensions as plugins?

See my reply in the topic Sorely confused about “Extensions”. I think it answers your question, but myself or others here can clarify further if need be.