feat: Add basic theme feature

layouts/partials/helpers/get-esbuild-options.html

@@ -69,15 +69,24 @@ params:
         #  id: foo
         #  name: bar
     
-    # The `darkMode` feature
+    # The `darkMode` feature. It's a deprecated setting but keep backward compatibility 
     darkmode:
       enable: true
 
+    # Configure theme settings
+    theme:
+      enable: true
+      services:
+        light: true # enable light theme. default "true"
+        dark: true # enable dark theme. default "true"
+        defaultTheme: light # can be either light, dark or system. default "system"
+
 This helper will convert the above config into the following env vars:
 
   * `FEATURE_ANALYTICS=1`
   * `FEATURE_ANALYTICS_GOOGLE=1`
   * `FEATURE_DARKMODE=1`
+  * `FEATURE_THEME=1`
 
 In JS, you can use it like this: