Add changelog for gzip mime type

Author: varunnvs92

.changes/next-release/feature-AWSSDKforJavav2-cea02db.json

@@ -0,0 +1,5 @@
+{
+    "category": "AWS SDK for Java v2", 
+    "type": "feature", 
+    "description": "Add application/gzip mime type"
+}