Add Marko

[tigt]

• Depends on Tweak some samples for clarity and better behavior in playgrounds #148 to be consistent with other frameworks — I have no problems editing them back if that doesn’t get merged, however
• Places Marko with the other resumable frameworks (if there’s other logic for how the frameworks are sorted, I’d love to know)
• Updated the contribution guidelines with what I had to figure out to get the Playground URL working
• Some of the Marko playground URLs produce interesting errors — those are bugs on our end, we’ll fix them out of band

[tigt]

Oh, uh, I’d be happy to fix up my WIP commit history if your repo doesn’t squash upon merge

[matschik]

Thanks a lot ! Hope we can find a solution to #148 PR, then I'll review it

[matschik]

If you can submit this PR without playground issues, we'll be able to add Marko.

[tigt]

Roger. Might be a little bit before I get that update in — just left eBay

[tigt]

Okay, I changed the Viewport Size and mixed checkbox examples back to Page Title and autofocused input.