[Editor] Adding links to other dashboards for navigation

[nicolaslara]

Based on the discussion on #15, we want to allow editors to add links to other dashboards.

I'm not sure if this is standard in superset. I'll investigate and if it isn't find a way to include it.

[nicolaslara]

This can be done by creating a markdown chart. I'll add it an example to the docs

[vturmine]

@nicolaslara I tested it with markdown syntax but the targeted link is loaded in the markup frame. It's working with HTLM syntax using "target=_blank".
Could you add it in the documentation?

[nicolaslara]

Sure, I'll add that to the docs.