Merge branch 'trusted-servers-doc' into 'next'

document `trusted_servers` option

See merge request famedly/conduit!451

conduit-example.toml

@@ -43,6 +43,10 @@ allow_federation = true
 # Enable the display name lightning bolt on registration.
 enable_lightning_bolt = true
 
+# Servers listed here will be used to gather public keys of other servers.
+# Generally, copying this exactly should be enough. (Currently, Conduit doesn't
+# support batched key requests, so this list should only contain Synapse
+# servers.)
 trusted_servers = ["matrix.org"]
 
 #max_concurrent_requests = 100 # How many requests Conduit sends to other servers at the same time