add examples and update readme

example/idgen_dart_example.dart

@@ -4,8 +4,9 @@ import 'package:teamhydra_idgen/teamhydra_idgen.dart';
 void main() async {
   IDGen idgen = IDGen(username: 'your_username', token: 'your_token');
 
-  // Generate a new ID, in this example we are generating a UUID V4
-  IDGenResponse uuid =
-      await idgen.generateUUIDV4(); // all generations are async
-  print('Generated UUID: ${uuid.id}'); // print the generated ID
+  // A more complex example can be generating a new IDs with a specific alphabet
+  // and length
+  IDGenResponse newID = await idgen.generateNanoID(
+      alphabet: 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789', size: 20);
+  print('New ID: ${newID.id}');
 }