Add peripheral_hub type for wired-modem-like peripherals (#1193)

This allows other mods to create wired-modem alike blocks, which expose
peripherals on the wired network, without having to reimplement the main
modem interface.

This is not currently documented, but a peripheral_hub should provide
the following methods:

 - isPresentRemote
 - getTypeRemote
 - hasTypeRemote
 - getMethodsRemote
 - callRemote

src/main/java/dan200/computercraft/shared/peripheral/modem/wired/WiredModemPeripheral.java

@@ -72,6 +72,13 @@ public abstract class WiredModemPeripheral extends ModemPeripheral implements IW
     protected abstract WiredModemLocalPeripheral getLocalPeripheral();
     //endregion
 
+    @Nonnull
+    @Override
+    public Set<String> getAdditionalTypes()
+    {
+        return Collections.singleton( "peripheral_hub" );
+    }
+
     //region Peripheral methods
 
     /**