Add inline syntax errors to website editor

[bvaughn]

Proof of concept by @tsriram:

Some discussion on facebook/react/issues/11094

Currently blocking on FormidableLabs/react-live#41

[el1f]

Hasn't this already been tackled by now?

[bvaughn]

The description says this issue is blocked by FormidableLabs/react-live#41 which is unresolved. If you'd like to see this happen, contribute a PR to react-live first to unblock this issue 😄