Support markdown tables in annotations

[bjeanes]

It'd be great to be able to express tabular output in annotations from markdown (which is easy to generate from scripts):

Not urgent, as I can workaround by generating HTML:

[ticky]

@bjeanes we’ve updated our Markdown renderer to handle this syntax!

You should be able to use most GitHub Flavored Markdown features now, aside from syntax highlighting, task lists, user mentions, and automatic links for references to issues, pull requests or commits.

[bjeanes]

@ticky yay that was fast. Thank you