feat: Support Dark mode for the widget (#4137)

Co-authored-by: Pranav Raj S <pranav@chatwoot.com>

app/javascript/widget/store/modules/appConfig.js

@@ -15,6 +15,7 @@ const state = {
   showPopoutButton: false,
   widgetColor: '',
   widgetStyle: 'standard',
+  darkMode: 'light',
 };
 
 export const getters = {
@@ -25,18 +26,26 @@ export const getters = {
   getWidgetColor: $state => $state.widgetColor,
   getReferrerHost: $state => $state.referrerHost,
   isWidgetStyleFlat: $state => $state.widgetStyle === 'flat',
+  darkMode: $state => $state.darkMode,
 };
 
 export const actions = {
   setAppConfig(
     { commit },
-    { showPopoutButton, position, hideMessageBubble, widgetStyle = 'rounded' }
+    {
+      showPopoutButton,
+      position,
+      hideMessageBubble,
+      widgetStyle = 'rounded',
+      darkMode = 'light',
+    }
   ) {
     commit(SET_WIDGET_APP_CONFIG, {
       hideMessageBubble: !!hideMessageBubble,
       position: position || 'right',
       showPopoutButton: !!showPopoutButton,
       widgetStyle,
+      darkMode,
     });
   },
   toggleWidgetOpen({ commit }, isWidgetOpen) {
@@ -56,6 +65,7 @@ export const mutations = {
     $state.position = data.position;
     $state.hideMessageBubble = data.hideMessageBubble;
     $state.widgetStyle = data.widgetStyle;
+    $state.darkMode = data.darkMode;
   },
   [TOGGLE_WIDGET_OPEN]($state, isWidgetOpen) {
     $state.isWidgetOpen = isWidgetOpen;