Make the rich-text editor components have better (noneditable) previews

[AllanYangZhou]

Currently the rich-text component previews in the rich text editor are tiny icons. Ideally, these should resemble the actual learner's view instead.

The preview itself should not be editable, so we should investigate the possibility of using a non-editable 'island' within a contenteditable as our preview.

[seanlip]

Hi @virajprabhu -- did you manage to take a look at this? If you need any help, please say!

[virajprabhu]

Hi @seanlip - sorry, I haven't been able to get time to look at this. If this is high priority, could you please get someone else to take it on? I don't think I'll be able to work on this for another couple of weeks.

[seanlip]

Update -- from a meeting @kahkhang, @AllanYangZhou and I had, we decided to just make Tabs, Collapsible, Image and Video into big blocks for now, and, in general, handle this issue via baby steps. A one-size-fits-all solution seems to be running into lots of problems (see #1426 and this doc), and doesn't seem feasible due to bugs in the underlying technologies (Firefox, textAngular).

[seanlip]

Superseded by #1810 and #1811. Closing.