OnBoarding main screen: Use the custom Lato font for the heading

I'm not sure if I should use this font all over, or if just in this
place.

lib/screens/onboarding_screens.dart

@@ -225,6 +225,8 @@ class OnBoardingInitialChoice extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    var headerTextStyle =
+        Theme.of(context).textTheme.display3.copyWith(fontFamily: "Lato");
     var header = Row(
       children: <Widget>[
         Image.asset(
@@ -234,7 +236,7 @@ class OnBoardingInitialChoice extends StatelessWidget {
         ),
         Text(
           "GitJournal",
-          style: Theme.of(context).textTheme.display3,
+          style: headerTextStyle,
         ),
       ],
     );

pubspec.yaml

@@ -26,6 +26,10 @@ flutter:
     - "assets/icon/icon.png"
     - "assets/icon/github-icon.png"
     - "assets/icon/gitlab-icon.png"
+  fonts:
+    - family: Lato
+      fonts:
+        - asset: fonts/Lato-Regular.ttf
 
 flutter_icons:
   android: "launcher_icon"