Add feature to have checkboxes or tasklists as in GitHub flavored Markdown

[dtchanpura]

GitHub markdown supports creation of checkboxes by writing [ ] (space inside square brackets) and selected checkbox by [x] (x inside square brackets)

Just like as follows

- [ ] not selected
- [x] selected

So in case when converted to HTML it should be something like ...

<ul>
<li><input type="checkbox">not selected</li>
<li><input type="checkbox" checked>selected</li>
</ul>

Reference: https://blog.github.com/2014-04-28-task-lists-in-all-markdown-documents/
Reference: fabiocolacio/Marker#218

[faywong]

It's reasonable to support tasklists.

[smithfred]

Would be better to support the full set of GFM extensions if possible, since it's a widely used set of extensions (and is fully specified against CommonMark).

[000exploit]

Feature still not implemented?