Fix parallax size (#800)

* Non-fullscreen ParallaxComponent

* Updated examples with no size needed

* Formatting

* Add docs for fullscreen parallax

* Fix formatting

* Remove need of nullable size

* Add basic parallax sizing test

* Fix formatting

* Remove unused imports

* Info text for the parallax examples

scripts/check_coverage.dart

@@ -3,8 +3,8 @@ import 'dart:io';
 void main(args) {
   final coverageSummary = args[0] as String;
   final currentRaw = coverageSummary.replaceFirstMapped(
-      RegExp(r".* (\d+\.\d+)%.*"), 
-      (matches) => '${matches[1]}',
+    RegExp(r".* (\d+\.\d+)%.*"),
+    (matches) => '${matches[1]}',
   );
 
   final current = double.parse(currentRaw);