Update README.md

Author: mtj0928

README.md

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 # typed-notifications
+
+<p align="center">
+    <img width="280" alt="logo" src="https://github.com/user-attachments/assets/935a0d73-6dd2-47e5-8846-f1449dbf7f73">
+</p>
+<p align="center">
+    <strong>typed-notifications</strong><br>
+    This library attaches type-information to NotificationCenter.
+</p>
+
+
 This library attaches type-information to `NotificationCenter`.
 You can post and observe notifications in a type-safe manner.