Add Sentry logo in the README (#604)

Author: HazAT

README.md

@@ -1,3 +1,10 @@
+<p align="center">
+  <a href="https://sentry.io" target="_blank" align="center">
+    <img src="https://sentry-brand.storage.googleapis.com/sentry-logo-black.png" width="280">
+  </a>
+  <br />
+</p>
+
 # sentry-symfony
 
 Symfony integration for [Sentry](https://getsentry.com/).