fix typo in manual config

doc/manual-config.md

 # Manual configuration
 
-To add mnually configuration parameters to Duniter, use `config` command:
+To add manually configuration parameters to Duniter, use `config` command:
 
 ```bash
 $ duniter config
@@ -99,4 +99,4 @@ $ duniter start
 Signed requests with PGP: enabled.
 Duniter server listening on 127.0.0.1 port 8888
 Duniter server listening on ::1 port 8888
-```
\ No newline at end of file
+```