Bump version; Update changelog

CHANGELOG.md

@@ -1,6 +1,12 @@
 # Changelog
 
-# v2.1.5
+## v2.2.0
+
+- Optimized memory usage. [Memory usage tweaks](./docs/memory_usage_tweaks.md);
+- `Vary` header is set when WebP detection, client hints or GZip compression are enabled;
+- Health check doesn't require `Authorization` header anymore.
+
+## v2.1.5
 
 - [Sentry support](./docs/configuration.md#error-reporting) (thanks to [@koenpunt](https://github.com/koenpunt));
 - Fixed detection of some kind of WebP images;

main.go

@@ -11,7 +11,7 @@ import (
 	_ "net/http/pprof"
 )
 
-const version = "2.1.5"
+const version = "2.2.0"
 
 type ctxKey string