feat: ThemeBuilder support for dark themes.

catalyst_voices/packages/catalyst_voices_brands/lib/src/theme_builder/theme_builder.dart

@@ -8,19 +8,30 @@ import 'package:flutter/material.dart';
 /// [buildTheme] can be used to obtain the corresponding theme data for the
 /// [BrandKey] passed to the method.
 /// 
+/// [buildDarkTheme] operates in the same way but picks the dark version of the
+/// theme for a specific brand. 
+/// 
 /// For each brand there is a specific key defined in the [BrandKey] enum 
 /// and a corresponding [ThemeData] in the `themes` folder.
+/// For each brand a light and a dark [ThemeData] should be defined.
 ///
-/// [buildTheme] defaults to the [catalyst] theme. 
+/// [buildTheme] and [buildDarkTheme] default to the [catalyst] theme.
 class ThemeBuilder {
+  static final Map<BrandKey, ThemeData> lightThemes = {
+    BrandKey.catalyst: catalyst,
+    BrandKey.fallback: fallback,
+  };
+
+  static final Map<BrandKey, ThemeData> darkThemes = {
+    BrandKey.catalyst: darkCatalyst,
+    BrandKey.fallback: darkFallback,
+  };
+
   static ThemeData buildTheme(BrandKey? brandKey) {
-    switch (brandKey) {
-      case BrandKey.catalyst:
-        return catalyst;
-      case BrandKey.fallback:
-        return fallback;
-      case null:
-        return catalyst;
-    }
+    return lightThemes[brandKey ?? BrandKey.catalyst]!;
+  }
+
+  static ThemeData buildDarkTheme(BrandKey? brandKey) {
+    return darkThemes[brandKey ?? BrandKey.catalyst]!;
   }
 }

catalyst_voices/packages/catalyst_voices_brands/lib/src/themes/catalyst.dart

@@ -8,3 +8,5 @@ final ThemeData catalyst = ThemeData(
     primary: VoicesColors.blue,
   ),
 );
+
+final ThemeData darkCatalyst = ThemeData.dark();

catalyst_voices/packages/catalyst_voices_brands/lib/src/themes/fallback.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
 
 /// [ThemeData] for the `fallback` brand.
-final ThemeData fallback = ThemeData(useMaterial3: true);
+final ThemeData fallback = ThemeData.light();
+final ThemeData darkFallback = ThemeData.dark();

catalyst_voices/packages/catalyst_voices_brands/test/src/catalyst_voices_brands_test.dart

@@ -43,6 +43,7 @@ void main() {
             ),
           ),
           theme: ThemeBuilder.buildTheme(state.brandKey),
+          darkTheme: ThemeBuilder.buildTheme(state.brandKey),
         );
       },
     ),