Allow 16 lines of text in the rich text editors

[artcodespace]

This PR increases the max-height of the relevant container to allow the rich text editor to display up to 16 lines of text before scrolling starts.

Displayed are before and afters for the rich text editor (both modes) and the current composer (to check nothing has changed there)

Checklist

• Tests written for new code (and old code if feasible)
• Linter and other CI checks pass
• Sign-off given on the changes (see CONTRIBUTING.md)

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Here's what your changelog entry will look like:

✨ Features

• Allow 16 lines of text in the rich text editors (#10670). Contributed by @alunturner.

[germain-gg]

It looks like there's a few bits that are hardcoding 22px in this file too. min-height just a few lines above being a good example.

That looks good in principle but I'm a bit worried about the connection with _Editor.pcss and how easily this might get thrown out the window. But I'm not sure I can think of a much better way to connect these two

[artcodespace]

What do you mean by thrown out of the window? As in it forces something useful offscreen?

I've played around with it in a browser at different zoom levels and in it's current guise, it was usable at full height up to 200% zoom on a laptop (16" screen). Do we have any aims in terms of the zoom levels we try to support?

Usability can be increased by doing something like

      @media screen and (max-height: 550px) {
                .mx_WysiwygComposer_Editor_content {
                    max-height: calc(8 * $font-22px);
                }
            }

To help us out on tiny screens (effectively how Chrome seems to represent heavily zoomed in views). The snippet above would keep it usable to 300% zoom.