Update for Gnome 40 - Ubuntu 21.10

[bytersproblem]

###Linux Distribution version

Ubuntu 21.10

###Gnome Shell version

40.05

###Xorg or Wayland (or both)

n/a

###Extension version or branch

n/a

###Description of the problem

The extension does not work under Gnome-shell 40 in Ubuntu 21.10

###Steps to reproduce the problem

unzip the extension to ~/.local/share/gnome-shell/extensions/... the extension is visible in the extensions application but cannot be started. The log trace of the error:

Error: No property border_width on WorkspacesToDockPreferencesWidget

Stack trace:
  _init/Gtk.Widget.prototype._init@resource:///org/gnome/gjs/modules/core/overrides/Gtk.js:45:40
  _parent@resource:///org/gnome/gjs/modules/script/_legacy.js:40:21
  _init@/home/borivoje/.local/share/gnome-shell/extensions/[email protected]/prefs.js:30:14
  wrapper@resource:///org/gnome/gjs/modules/script/_legacy.js:83:27
  buildPrefsWidget@/home/borivoje/.local/share/gnome-shell/extensions/[email protected]/prefs.js:2303:18
  _init@resource:///org/gnome/Shell/Extensions/js/extensionsService.js:209:40
  OpenExtensionPrefsAsync/<@resource:///org/gnome/Shell/Extensions/js/extensionsService.js:122:28
  asyncCallback@resource:///org/gnome/gjs/modules/core/overrides/Gio.js:115:22
  run@resource:///org/gnome/Shell/Extensions/js/dbusService.js:177:20
  main@resource:///org/gnome/Shell/Extensions/js/main.js:19:13
  run@resource:///org/gnome/gjs/modules/script/package.js:206:19
  start@resource:///org/gnome/gjs/modules/script/package.js:190:8
  @/usr/share/gnome-shell/org.gnome.Shell.Extensions:1:17

This extension is a must-have, so it would be nice if developers thought of keeping it alive for all future versions of gnome-shell.

Thanks for your work!