chore: Improvements to utils to load article in widget (#7859)

app/javascript/widget/mixins/darkModeMixin.js

@@ -3,6 +3,12 @@ import { mapGetters } from 'vuex';
 export default {
   computed: {
     ...mapGetters({ darkMode: 'appConfig/darkMode' }),
+    prefersDarkMode() {
+      const isOSOnDarkMode =
+        this.darkMode === 'auto' &&
+        window.matchMedia('(prefers-color-scheme: dark)').matches;
+      return isOSOnDarkMode || this.darkMode === 'dark';
+    },
   },
   methods: {
     $dm(light, dark) {