Add UpperCaseInput formatter

lib/extensions/input_formatter.dart

@@ -0,0 +1,12 @@
+import "package:flutter/services.dart";
+
+class UpperCaseTextFormatter extends TextInputFormatter {
+  @override
+  TextEditingValue formatEditUpdate(
+      TextEditingValue oldValue, TextEditingValue newValue) {
+    return TextEditingValue(
+      text: newValue.text.toUpperCase(),
+      selection: newValue.selection,
+    );
+  }
+}