updated documentation

etc/alice-lg/alice.example.conf

@@ -42,6 +42,11 @@ stream_parser_throttle = 30000
 
 # [postgres]
 # url = "postgres://postgres:postgres@localhost:5432/alice"
+
+# As an alternative to the url, you can use the environment variables
+# from libpq to configure the postgres connection:
+# https://www.postgresql.org/docs/current/libpq-envars.html
+
 # min_connections = 2
 # max_connections = 128