Add a server-sided way to remove color codes from incoming chat messages (#5948)

These code be generated by CSM, a modded client or just copy and pasted by the player.

Changes
- Update configuration example and setting translation file.
- Remove colour codes before logging chat.
- Add setting to remove colour codes before processing the chat.

src/defaultsettings.cpp

@@ -252,6 +252,7 @@ void set_default_settings(Settings *settings)
 
 	// Server
 	settings->setDefault("disable_escape_sequences", "false");
+	settings->setDefault("strip_color_codes", "false");
 
 	// Network
 	settings->setDefault("enable_ipv6", "true");