Document XML extensions availability

Author: thekid

ChangeLog.md

@@ -3,6 +3,10 @@ AWS Lambda change log
 
 ## ?.?.? / ????-??-??
 
+* Merged PR #11: Enable XML extensions. The PHP extensions dom, libxml,
+  xml, xmlreader and xmlwriter are now available. See discussion in #8
+  (@thekid)
+
 ## 2.2.0 / 2021-09-15
 
 * Implemented feature request #9: Add podman support - @thekid