Refactored Embed

[oskarkrawczyk]

Embed is a bit dated at this point as it follows UI and code from JSFiddle 2.0.

A few ideas:

• Split view - It would be good to refactor the UI, along with adding a split-view where the RESULTS can be visible along one of the code panels (JS, HTML, CSS).
• Simplified editing - Another good feature would be a simplified way of editing inside of the embed - this would require the usage of CodeMirror inside of the embed and while that's additional kilobytes to download, the upside is that syntax coloring would be already there, no need to use the external library we have right now.
• Loading optimization - lazy load the iframe itself and the results iframe, perhaps there are further optimizations that could be made.
• Auto light-dark theme - following the theme of the parent website where the embed is... embedded.

Needs fixing:

• body color doesn't work with iFrame embeds #1832