Add zsh completions

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

hosts/common/configs/user/gui/theme/theme.completion.sh

@@ -0,0 +1,11 @@
+_theme-completion() {
+  local options=(
+    '-m[set mode: light, dark, or toggle]:mode:(light dark toggle)'
+    '-w[set wallpaper: specify file path]:file:_files'
+  )
+  local curcontext="$curcontext" state line
+  typeset -A opt_args
+  _arguments -s $options
+}
+
+compdef _theme-completion theme