Responsive permissions page

[Samq64]

Resolves #6844
Resolves #7464 (comment)

Changes

Makes the permissions page responsive, adds a scrollbar and fixes the button text.

Reason for changes

The permissions page was not designed for phones or short screens.

Tests

Tested on Chromium. Since I didn't put the scrollbar on the body it won't necessarily be on the edge of the window. The image is also slightly too wide for the IPhone SE in devtools.

[mxmou]

The image is also slightly too wide for the IPhone SE in devtools.

This can be fixed by changing

#screenshot {
  height: 10rem;
}

to

#screenshot {
  width: 24rem;
  max-width: 100%;
}