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

nitter.conf

@@ -28,6 +28,7 @@ tokenCount = 10
 # the limit gets reset every 15 minutes, and the pool is filled up so there's
 # always at least $tokenCount usable tokens. again, only increase this if
 # you receive major bursts all the time
+enableRSS = true  # set this to false to disable RSS feeds
 
 # Change default preferences here, see src/prefs_impl.nim for a complete list
 [Preferences]