Update changelog (#240)

Author: nicolas-grekas

Diff for: CHANGELOG.md

@@ -2,6 +2,12 @@
 
 All notable changes to this project will be documented in this file, in reverse chronological order by release.
 
+## 1.7.0
+
+- Bump to PHP 7.2 minimum
+- Allow psr/http-message v2
+- Use copy-on-write for streams created from strings
+
 ## 1.6.1
 
 - Security fix: CVE-2023-29197