Format Code and Add Format Checks to CI (#643)

* Remove unused lib/generated/i18n.dart

* Use `fvm dart format .`

* Add contributing guidelines

* Enforce dart format

* Add `dart format off` directive to generated files

lib/app_colors.dart

@@ -4,7 +4,6 @@ import "package:inventree/helpers.dart";
 import "package:one_context/one_context.dart";
 
 bool isDarkMode() {
-
   if (!hasContext()) {
     return false;
   }