Add task list support `- [ ] `

[adrianthedev]

Marksmith currently doesn't support task lists.
We can add support for that in the renderer.

[timwis]

Hey @adrianthedev 👋🏻
I was just looking into this and thought I'd share what I found: it looks like commonmarker has the tasklist extension enabled by default. The reason it wasn't rendering for me is because I was removing the <input> tag with my sanitize call. If I modify my sanitize call to allow the input tag, along with the type, checked, and disabled attributes, it renders the task list as expected. Of course, I'm not sure I want to allow all that, so perhaps a custom Loofah scrubber is in order. Will share if I get that working, but thought I'd leave this comment in the meantime.

(Also, this is just for commonmarker, not redcarpet)

[adrianthedev]

Would you mind sending in a PR with this tweak? I'd love to support it!