Add note about sync pruning to README

README.md

@@ -69,6 +69,8 @@ Medium priority:
    have it as part of the server itself
 
 Nice to have:
+ - **Pruning**: syncs never expire; either a background job or a standalone tool is needed to make cleanup operations
+   simpler
  - **Front page**: serving a static HTML page on `/`, perhaps with some simple JS to show the service status, should be
    fairly straightforward and would improve the end user experience. The main blocker here is my lack of design skills
    to craft a half decent looking front page