[#23, Fix #80] Move themes into the prompt module

modules/prompt/init.zsh

@@ -0,0 +1,19 @@
+#
+# Loads prompt themes.
+#
+# Authors:
+#   Sorin Ionescu <sorin.ionescu@gmail.com>
+#
+
+# Load and run the prompt theming system.
+autoload -Uz promptinit && promptinit
+
+# Load the prompt theme.
+zstyle -a ':omz:module:prompt' theme 'prompt_argv'
+if (( $#prompt_argv > 0 )); then
+  prompt "$prompt_argv[@]"
+else
+  prompt 'off'
+fi
+unset prompt_argv
+