chromebook: add xkb options for neo2 layout on chromebooks

To support neo2 layout on chromebooks, activate the standard ralt_switch
option ("Key to choose 5th Level" -> "Right Alt chooses 5th level") as
well as the lwin_switch option included in this commit ("Chromebook
options" -> "Left Win chooses 3rd level").

For Gnome, they can be activated in the Gnome Tweak tool ("Keyboard &
Mouse" -> "Additional Layout Options").

chromebook/.config/xkb/rules/evdev

@@ -0,0 +1,4 @@
+! option = symbols
+  chromebook:swap_lwin_caps    = +chromebook(swap_lwin_caps)
+  chromebook:lwin_switch       = +chromebook(lwin_switch)
+! include %S/evdev

chromebook/.config/xkb/rules/evdev.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE xkbConfigRegistry SYSTEM "xkb.dtd">
+<xkbConfigRegistry version="1.1">
+  <optionList>
+    <group allowMultipleSelection="true">
+      <configItem>
+        <name>chromebook</name>
+        <description>Chromebook options</description>
+      </configItem>
+      <option>
+      <configItem>
+        <name>chromebook:swap_lwin_caps</name>
+        <description>Swap Search Key and CAPS</description>
+      </configItem>
+      </option>
+      <option>
+      <configItem>
+        <name>chromebook:lwin_switch</name>
+        <description>Left Win chooses 3rd level</description>
+      </configItem>
+      </option>
+    </group>
+  </optionList>
+</xkbConfigRegistry>

chromebook/.config/xkb/symbols/chromebook

@@ -0,0 +1,18 @@
+// Swap the functions of the left Win key (Search) and the CAPS key.
+partial modifier_keys
+xkb_symbols "swap_lwin_caps" {
+  replace key <LWIN> { [ Caps_Lock ] };
+  replace key <CAPS> { [ Super_L ] };
+  // modifier_map Mod3  { <LWIN> };
+};
+
+// Use LWIN as modifier key
+partial modifier_keys
+xkb_symbols "lwin_switch" {
+  key <LWIN> {
+    type[Group1]="ONE_LEVEL",
+    symbols[Group1] = [ ISO_Level3_Shift ]
+  };
+  include "level3(modifier_mapping)"
+};
+