Add enableRSS setting in config file

Useful for instance owners who want to disable the RSS endpoint for
reasons such as abuse and not enough server resources to handle heavy
network traffic through that endpoint.

Resolves #437

src/nitter.nim

@@ -46,7 +46,8 @@ createStatusRouter(cfg)
 createSearchRouter(cfg)
 createMediaRouter(cfg)
 createEmbedRouter(cfg)
-createRssRouter(cfg)
+if cfg.enableRSS:
+  createRssRouter(cfg)
 
 settings:
   port = Port(cfg.port)