Apply typehints to pocketmine\network\mcpe\protocol namespace

this is pulled from network-nuke in order to reduce the size of the diff.

src/pocketmine/network/mcpe/protocol/ServerSettingsRequestPacket.php

@@ -30,11 +30,11 @@ use pocketmine\network\mcpe\NetworkSession;
 class ServerSettingsRequestPacket extends DataPacket{
 	public const NETWORK_ID = ProtocolInfo::SERVER_SETTINGS_REQUEST_PACKET;
 
-	protected function decodePayload(){
+	protected function decodePayload() : void{
 		//No payload
 	}
 
-	protected function encodePayload(){
+	protected function encodePayload() : void{
 		//No payload
 	}