Docs: updating demos CSS.

[godai78]

Suggested merge commit message (convention)

Docs: updating demos CSS. Closes #14995

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Additional information

Merge together with https://github.com/cksource/ckeditor5-commercial/pull/5514

[Witoso]

• The inline editor example is still jumping, I think classes need to be added to all direct containers of the editor, e.g. header. Not sure, as maybe a different CSS styles it.
• Classic behaves perfectly, full-featured is also a classic but the image jumps left to right (better than right now, anyway). My bad didn't have the commercial repo updated. Thanks @pszczesniak .

[godai78]

This one is hard, adding the class to the very container holding the affected content made things even worse.

Adding a loader class (like we do in CF) to postpone display before loading did nothing at all.

I changed the image alignment to the left, so it jumps a little less, but I can come up with no handy solution for that.

We might consider putting it into a follow up, if we want global changes fast. We may also give up the image, but that's an unpreferred solution.

[Witoso]

Good for me 👍