[Docs] Improved RWD of demos in Examples section

[dkonopka]

Suggested merge commit message (convention)

Docs: Improved RWD of demos in the Examples section. Closes #5598.

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Additional information

1. Enlarged container width of document editor demo

2. Fixed document editor demo for mobiles because ATM it looks like this:

Before:

[oleq]

It looks better but there's still some weird movement at some point

[Reinmar]

Enlarged container width of document editor demo

Could we keep the textual content limited to some max-width there? So only the editor stretches? I think that this is the only demo where we need something like this, so it can be hardcoded there, I guess...

[oleq]

Could we keep the textual content limited to some max-width there?

I'm confused. Isn't it exactly what Damian did below?

[dkonopka]

I'm confused. Isn't it exactly what Damian did below?

@Reinmar means title & paragraph above the editor. But it's not easiest thing to do, because we can't "catch" these elements easily...

.main__content-inner .main__content-title,
.main__content-inner > p {
  max-width: some-number;
}

[dkonopka]

@Reinmar I'm not so sure about this change: