chore(meta): add contributor list to README (#902)

Co-authored-by: Michi Hoffmann <cleptric@users.noreply.github.com>

README.md

@@ -51,12 +51,16 @@ try {
 }
 ```
 
-## Symfony Version Compatibility
-
 ## Contributing to the SDK
 
 Please refer to [CONTRIBUTING.md](CONTRIBUTING.md).
 
+### Thanks to all the people who contributed so far!
+
+<a href="https://github.com/getsentry/sentry-symfony/graphs/contributors">
+  <img src="https://contributors-img.web.app/image?repo=getsentry/sentry-symfony" />
+</a>
+
 ## Getting help/support
 
 If you need help setting up or configuring the Symfony SDK (or anything else in the Sentry universe) please head over to the [Sentry Community on Discord](https://discord.com/invite/Ww9hbqr). There is a ton of great people in our Discord community ready to help you!
@@ -76,3 +80,4 @@ Licensed under the MIT license, see [`LICENSE`](LICENSE)
 [Packagist link]: https://packagist.org/packages/sentry/sentry-symfony
 [Master Code Coverage]: https://codecov.io/gh/getsentry/sentry-symfony/branch/master
 [Master Code Coverage Image]: https://img.shields.io/codecov/c/github/getsentry/sentry-symfony/master?logo=codecov
+