Update changelog for 2.2 release (#2952)

Author: XWB

Changelog.md

@@ -1,10 +1,22 @@
 Changelog
 =========
 
-### 2.2.0 (2020-xx-xx)
+### 2.2.0 (2020-01-xx)
+=======
 
 * Marked all controllers final.
 * Added Mongolian translation.
+* Added an email provider.
+* Added a custom user checker.
+* Added PHP 7.3 support.
+* Removed fieldName attribute in MongoDB mapping.
+* Registration confirmation now redirects to login page if token is invalid.
+* User model will not rely on `AdvancedUserInterface` anymore.
+* Self-salting password encoders will not create a salt anymore.
+* FlashListener constructor now accepts `SessionInterface`.
+* Fixed `UserManagerInterface::updateUser` signature.
+* Fixed several Symfony deprecation notices.
+* Fixed several translations.
 
 ### 2.1.2 (2018-03-08)