Fix kiwi://extensions on small screens

[bershanskiy]

This was not tested on real build yet (waiting for CI)

This PR fixes visual issues of kiwi://extensions on small screens (less than 400 virtual pixels):

• the developer toggle is not visible because the label itself takes its place
  There was a way to access the toggle, but it was not intuitive (click on "search" icon to hide page label, then hold and swipe the toggle).
• the extension cards are too wide and do not fit the screen

Before

Screenshot made on Kiwi 105.0.5195.33 on Samsung Galaxy S20 FE:

After:

Screenshot made on Chromium on PC (real Kiwi screenshot coming later):

[bershanskiy]

@kiwibrowser I would appreciate if you could trigger CI build, since GitHub Actions on my fork do not have necessary token and I couldn't find docs about building Kiwi from full source on Linux (or any other platform).

[bershanskiy]

This is basically a "hello world" PR to test out build system and process while fixing a minor thing.

[Huge]

Fairly good, have not tested myself either, though.

[Huge]

*hide the toggle label to leave space

[Huge]

not sure setting a (large enough though )constant is a good practice.

[Huge]

Great effort!
Seems you have missed that src.next is made by the same team as the old src KiwiBrowser, where there is extensive guide, I'm just going through it.
Please join https://matrix.to/#/#kiwibrowser-fans-building-it:matrix.org to talk/coordinate our efforts!+)