Move Themes to their own file

I'm just experimenting with having different components more neatly
separated.

analysis_options.yaml

@@ -51,7 +51,7 @@ linter:
     # - avoid_as
     # - avoid_catches_without_on_clauses # not yet tested
     # - avoid_catching_errors # not yet tested
-    - avoid_classes_with_only_static_members
+    # - avoid_classes_with_only_static_members
     # - avoid_function_literals_in_foreach_calls # not yet tested
     - avoid_init_to_null
     - avoid_null_checks_in_equality_operators

lib/app.dart

@@ -5,6 +5,7 @@ import 'package:fimber/fimber.dart';
 import 'package:firebase_analytics/firebase_analytics.dart';
 import 'package:firebase_analytics/observer.dart';
 import 'package:flutter/material.dart';
+
 import 'package:journal/apis/git.dart';
 import 'package:journal/screens/home_screen.dart';
 import 'package:journal/screens/settings_screen.dart';
@@ -12,6 +13,8 @@ import 'package:journal/settings.dart';
 import 'package:journal/state_container.dart';
 import 'package:journal/utils.dart';
 import 'package:journal/appstate.dart';
+import 'package:journal/themes.dart';
+
 import 'package:shared_preferences/shared_preferences.dart';
 import 'package:dynamic_theme/dynamic_theme.dart';
 
@@ -89,25 +92,7 @@ class JournalApp extends StatelessWidget {
   Widget build(BuildContext context) {
     return DynamicTheme(
       defaultBrightness: Brightness.light,
-      data: (brightness) {
-        if (brightness == Brightness.light) {
-          return ThemeData(
-            brightness: Brightness.light,
-            primaryColor: Color(0xFF66bb6a),
-            primaryColorLight: Color(0xFF98ee99),
-            primaryColorDark: Color(0xFF338a3e),
-            accentColor: Color(0xff6d4c41),
-          );
-        } else {
-          return ThemeData(
-            brightness: Brightness.dark,
-            primaryColor: Color(0xFF66bb6a),
-            primaryColorLight: Color(0xFF98ee99),
-            primaryColorDark: Color(0xFF338a3e),
-            accentColor: Color(0xff6d4c41),
-          );
-        }
-      },
+      data: (b) => b == Brightness.light ? Themes.light : Themes.dark,
       themedWidgetBuilder: buildApp,
     );
   }

lib/themes.dart

@@ -0,0 +1,19 @@
+import 'package:flutter/material.dart';
+
+class Themes {
+  static final light = ThemeData(
+    brightness: Brightness.light,
+    primaryColor: Color(0xFF66bb6a),
+    primaryColorLight: Color(0xFF98ee99),
+    primaryColorDark: Color(0xFF338a3e),
+    accentColor: Color(0xff6d4c41),
+  );
+
+  static final dark = ThemeData(
+    brightness: Brightness.dark,
+    primaryColor: Color(0xFF66bb6a),
+    primaryColorLight: Color(0xFF98ee99),
+    primaryColorDark: Color(0xFF338a3e),
+    accentColor: Color(0xff6d4c41),
+  );
+}