Non System fonts
I am trying to render a non system font (like OpenSans).

**Observed behavior:**
If you don't use a system font, then Sketch doesn't display the correct font and reports it as a "Missing Fonts" error, at top right of the application. Clicking the error allows you to replace the font.

Are we limited to system fonts? If so, Is there a way around this? 

I believe there is a way to move a 3rd party font into the system font, but heard its not advisable. Or is this my only route?
