Add 'compact density' support

[RealRaven2000]

In compact density mode, folders and messages are closer together; the menu items that represent folders (all popups triggered by QuickFolders tabs) should also allow for a similar density, based on the new menu font-size (see #394)

[RealRaven2000]

Test version below. This will only make menus denser that contain folder entries (the tools menus won't be affected). It is based on the menu font size which can be configured on the QuickFolders layout tab.

QuickFolders-mx-6.2pre44.zip

Magic rules:

:root[uidensity="compact"] .QuickFolders-folder-popup menuitem {
  min-height: 1.25em;
  padding-block: 2px;
}

[RealRaven2000]

Version for Thunderbird 102:

QuickFolders-mx-5.18pre14.zip

Restart maybe required to see layout changes (styles sheets are usually cached by Mozilla Browsers)

[RealRaven2000]

Implemented in 6.2 - Published 30/08/2023
also in 5.18 published 27/08/2023