doc: update readme

README.md

@@ -43,6 +43,8 @@ You can use contented as a standalone upload server, or you can use the SDK to e
         Title used in web interface (default "contented")
   -trustXForwardedFor
         Trust X-Forwarded-For reverse proxy headers
+  -concurrentthumbs
+        Simultaneous thumbnail generation (default 16)
 `
 
 If you are hosting behind a reverse proxy, remember to set its post body size parameter appropriately (e.g. `client_max_body_size` for nginx).
@@ -66,6 +68,10 @@ contented.init("#target", function(/* String[] */ items) {});
 
 =CHANGELOG=
 
+NEXT:
+- Feature: Option to limit concurrent thumbnail generation
+- Enhancement: Set charset=UTF-8 when serving user-submitted text/plain content
+
 2018-06-09: 1.2.1
 - Feature: Add OpenGraph tags on preview pages, for rich metadata in chat applications
 - Update thumbnailing library to improve quality