Add German layout variant e1_capslock_altgr

Hello everyone,

I propose to add another variant of the "German (E1)" keyboard layout: "German (E1, Caps Lock as AltGr)"

This variant uses the Caps Lock key as an additional "left" AltGr. The original Caps Lock function is available by pressing Ctrl + Caps Lock.

I am aware that the result is very similar to setxkbmap de e1 -option lv3:caps_switch.

I think this is useful because

• It makes typing {[]}~ on a German keyboard much more comfortable.

• Compared to the "lv3:caps_switch"-option, it has the added benefit of the Ctrl + Caps Lock combo.

• The 2023 DIN standard for German keyboards recommends it as an option:

  • https://de.wikipedia.org/wiki/E1_(Tastaturbelegung)#Feststelltaste/Umschaltsperre
  • https://en.wikipedia.org/wiki/Caps_Lock#Abolition