Allow link attributes in Markdown renderer

[nickjer]

Should enable link attributes in the Markdown renderer:

:link_attributes: hash of extra attributes to add to links.

This would allow things like:

[my link](https://myawesome.link){:target="_blank"}

Update: The above won't work as :link_attributes: is a hash of attributes that are applied to all links.

┆Issue is synchronized with this Asana task by Unito

[nickjer]

An alternative is to use https://kramdown.gettalong.org/ which is a superset of Markdown features that includes the above.

[ericfranz]

Tiny Bonus: Kramdown is a pure ruby parser, so that gets rid of another native extension to build.