Make REPL embeddable

[Rich-Harris]

Like jsfiddle — would be cool if you could embed the REPL output, or maybe a tabbed view showing component and JSON as well

[Ryuno-Ki]

I like, how CodePen does it.

[fskreuz]

@evs-chris created https://github.com/ractivejs/playground for Ractive which runs all the demos and tutorials in some areas of site (look for code blocks with a "Run It"). More inline than embedded though, but it's really close to a JSFiddle. 😄

Here's a sample https://ractive.js.org/concepts/data-management/#two-way-binding