D6113: Update helper docs for --windowed mode of plasmashell

[David Edmundson]

davidedmundson abandoned this revision.

REPOSITORY
  R120 Plasma Workspace

REVISION DETAIL
  https://phabricator.kde.org/D6113

To: davidedmundson, #plasma
Cc: mart, plasma-devel, ZrenBot, progwolff, lesliezhai, ali-mohamed, 
jensreuterberg, abetts, sebas, apol, lukas