D22933: [kcmkwin/kwindesktop] Improve the look of the Virtual Desktops KCM UI

GB_2 created this revision.
GB_2 added reviewers: KWin, Plasma, VDG.
Herald added a project: KWin.
Herald added a subscriber: kwin.
GB_2 requested review of this revision.

REVISION SUMMARY
  Apply the KDE HIG, make the list headers and desktop file consistent.
  F7160446: Improved Virtual Desktops KCM UI.png <https://phabricator.kde.org/F7160446>

TEST PLAN
  Open the Virtual Desktops KCM.

REPOSITORY
  R108 KWin

BRANCH
  improved-virtual-desktops-kcm-ui (branched from master)

REVISION DETAIL
  https://phabricator.kde.org/D22933

AFFECTED FILES
  kcmkwin/kwindesktop/kcm_kwin_virtualdesktops.desktop
  kcmkwin/kwindesktop/package/contents/ui/main.qml
  kcmkwin/kwindesktop/package/metadata.desktop
  kcmkwin/kwindesktop/virtualdesktops.cpp

To: GB_2, #kwin, #plasma, #vdg
Cc: #vdg, #plasma, kwin, #kwin, LeGast00n, sbergeron, jraleigh, fbampaloukas, GB_2, mkulinski, ragreen, jackyalcine, Pitel, iodelay, crozbo, bwowk, ZrenBot, ngraham, alexeymin, himcesjf, lesliezhai, ali-mohamed, hardening, romangg, jensreuterberg, abetts, sebas, apol, mart