Add changelog entries for unreleased changes

Author: stof

CHANGELOG.md

@@ -1,3 +1,9 @@
+## Unreleased
+
+* Add support for Symfony 7
+* Remove support for Symfony 4
+* Add support for env placeholders in the `level` option of handlers
+
 ## 3.8.0 (2022-05-10)
 
 * Deprecated ambiguous `elasticsearch` type, use `elastica` instead
@@ -18,7 +24,7 @@
 
 ## 3.7.0 (2021-03-31)
 
-* Use `ActivationStrategy` instead of `actionLevel` when available 
+* Use `ActivationStrategy` instead of `actionLevel` when available
 * Register resettable processors (`ResettableInterface`) for autoconfiguration (tag: `kernel.reset`)
 * Drop support for Symfony 3.4
 * Drop support for PHP < 7.1