Support dark theme in the example

example/lib/main.dart

@@ -18,12 +18,16 @@ class MyApp extends StatelessWidget {
         primarySwatch: Colors.blue,
         visualDensity: VisualDensity.adaptivePlatformDensity,
         useMaterial3: true,
+        brightness: Brightness.light,
       ),
-      // darkTheme: ThemeData(
-      //   primarySwatch: Colors.blue,
-      //   visualDensity: VisualDensity.adaptivePlatformDensity,
-      //   useMaterial3: true,
-      // ),
+      darkTheme: ThemeData(
+        primarySwatch: Colors.blue,
+        visualDensity: VisualDensity.adaptivePlatformDensity,
+        useMaterial3: true,
+        brightness: Brightness.dark,
+      ),
+      // ignore: avoid_redundant_argument_values
+      themeMode: ThemeMode.system,
       localizationsDelegates: [
         GlobalMaterialLocalizations.delegate,
         GlobalWidgetsLocalizations.delegate,

example/lib/pages/home_page.dart

@@ -202,15 +202,15 @@ class _HomePageState extends State<HomePage> {
           },
           customStyles: const DefaultStyles(
             h1: DefaultTextBlockStyle(
-                TextStyle(
-                  fontSize: 32,
-                  color: Colors.black,
-                  height: 1.15,
-                  fontWeight: FontWeight.w300,
-                ),
-                VerticalSpacing(16, 0),
-                VerticalSpacing(0, 0),
-                null),
+              TextStyle(
+                fontSize: 32,
+                height: 1.15,
+                fontWeight: FontWeight.w300,
+              ),
+              VerticalSpacing(16, 0),
+              VerticalSpacing(0, 0),
+              null,
+            ),
             sizeSmall: TextStyle(fontSize: 9),
           ),
           embedBuilders: [
@@ -234,15 +234,15 @@ class _HomePageState extends State<HomePage> {
         },
         customStyles: const DefaultStyles(
           h1: DefaultTextBlockStyle(
-              TextStyle(
-                fontSize: 32,
-                color: Colors.black,
-                height: 1.15,
-                fontWeight: FontWeight.w300,
-              ),
-              VerticalSpacing(16, 0),
-              VerticalSpacing(0, 0),
-              null),
+            TextStyle(
+              fontSize: 32,
+              height: 1.15,
+              fontWeight: FontWeight.w300,
+            ),
+            VerticalSpacing(16, 0),
+            VerticalSpacing(0, 0),
+            null,
+          ),
           sizeSmall: TextStyle(fontSize: 9),
           subscript: TextStyle(
             fontFamily: 'SF-UI-Display',
@@ -385,7 +385,6 @@ class _HomePageState extends State<HomePage> {
             Expanded(
               flex: 15,
               child: Container(
-                color: Colors.white,
                 padding: const EdgeInsets.only(left: 16, right: 16),
                 child: quillEditor,
               ),