feat: turn off KDE's middle-click paste

Inside a Chromium application the flag settles this on its own - with
autoscroll on, Blink stops pasting the primary selection. Everywhere else
on the desktop middle click goes on pasting, which is the thing this whole
program exists to get away from.

KWin has a switch for it, on Wayland, where the paste is a protocol the
compositor either offers or does not: EnablePrimarySelection in kwinrc.
Written with kwriteconfig, the way System Settings would, because kwinrc
has a cascade behind it. What the key said before goes in the ledger, so
disable puts it back - and a key that already said false is left alone and
not recorded, so a paste the user switched off themselves is never
switched back on.

X11 has no such switch and nothing is written there.

po/de.po

@@ -63,6 +63,9 @@ msgstr "%d – siehe Anwendungsliste"
 msgid "Steam"
 msgstr "Steam"
 
+msgid "Middle-click paste"
+msgstr "Mittelklick-Einfügen"
+
 msgid "New applications"
 msgstr "Neue Anwendungen"
 
@@ -112,6 +115,9 @@ msgstr "Programme, die sich beim Anmelden selbst starten"
 msgid "Spotify"
 msgstr "Spotify"
 
+msgid "Turn off KDE's middle-click paste"
+msgstr "KDEs Mittelklick-Einfügen abschalten"
+
 msgid "Apply to newly installed applications"
 msgstr "Auf neu installierte Anwendungen anwenden"
 
@@ -179,6 +185,9 @@ msgstr "Steam startet seine Oberfläche auf eine Art, die diese Version nicht ä
 msgid "Steam's interface cannot be given the flag without leaving a file Steam would reinstall; the change has been taken back."
 msgstr "Steams Oberfläche lässt sich das Flag nicht geben, ohne eine Datei zu hinterlassen, die Steam neu installieren würde; die Änderung wurde zurückgenommen."
 
+msgid "Middle click stops pasting at the next login."
+msgstr "Mittelklick fügt ab der nächsten Anmeldung nichts mehr ein."
+
 
 #. Help
 msgid "Usage: middleclick-autoscroll [command]"