Code blocks in tinymce could sometimes end up exploded into the sub
elements of the codemirror display.
This changes the strategy to render codemirror within the shadow dom of
a custom element while preserving the normal pre/code DOM structure.
Still a little instability when moving/adding code blocks within details
blocks but much harder to break things now.
- To display license info along with shortcuts.
- Extracted out plain layout from 503 error page.
- Added tests to ensure license references are as expected.
