nixos: make keyboard layout module opt-in

nix/nixosModules/extra/layouts/README.md

@@ -0,0 +1,41 @@
+This folder contains my very awesome dvorak French layout on linux
+
+# Ubuntu
+`$XDG_CONFIG_HOME/.config/xkb` doesn't work.
+[source](https://github.com/elias19r/xkb-layouts)
+
+NOTE: make sure the copied file has no extension, otherwise your x11 will crash.
+`# cp dvorak-french.xkb /usr/share/X11/xkb/symbols/`
+
+`/usr/share/X11/xkb/rules/evdev.xml`
+```xml
+<layoutList>
+...
+    <layout>
+        <configItem>
+            <name>dvorak-french</name>
+            <shortDescription>Baguette</shortDescription>
+            <description>French Dvorak</description>
+        </configItem>
+    </layout>
+...
+</layoutList>
+```
+
+`/usr/share/X11/xkb/rules/evdev.lst`
+```xml
+! layout
+  dvorak-french French Dvorak
+```
+
+## Swap escape and capslock
+`dconf write /org/gnome/desktop/input-sources/xkb-options "['caps:swapescape']"`
+(to undo, use `dconf reset`)
+
+# Notes
+Use `setxkbmap -option caps:swapescape` to swap escape and capslock
+It is possible to reset this option by using the `-option` flag without any argument.
+[source](https://askubuntu.com/a/830343)
+
+## Sources
+https://help.ubuntu.com/community/Custom%20keyboard%20layout%20definitions