adding migration guide

Author: mihaileu

README.md

@@ -20,9 +20,27 @@ Check the documentation in [ReadTheDocs](http://gearmanbundle.readthedocs.org/).
 Some recipes will be written soon. If you have some ideas and you want to share
 them with us, don't hesitate to open a RFC issue or a Pull Request.
 
+Migration from 4 to 5:
+```
+    doctrine_cache:
+        providers:
+            gearman_cache:
+                type: file_system
+                namespace: doctrine_cache.ns.gearman
+```
+needs to be replaced with
+```
+
+    framework:
+        cache:
+            pools:
+                gearman_cache:
+                    adapter: cache.adapter.filesystem
+```
 
 Tags
 ----
+* Symfony 5/6 is supported by tags 5
 * Symfony 4.0 is supported by tags 4.1+ (they still work with Symfony 3.X)
 * All 4.X tags support Symfony 3.X
 * Use tags lower than 4.X for Symfony 2.X versions