doc: Update README with missing metas.

Author: freezy

README.md

@@ -41,6 +41,9 @@ git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/o
 git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/win-x86/PinMame.dll.meta
 git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/win-x86/VisualPinball.Engine.PinMAME.dll.meta
 git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/win-x86/libpinmame-3.4.dll.meta
+git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/win-x64/PinMame.dll.meta
+git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/win-x64/VisualPinball.Engine.PinMAME.dll.meta
+git update-index --assume-unchanged VisualPinball.Engine.PinMAME.Unity/Plugins/win-x64/libpinmame-3.4.dll.meta
 ```
 
 ## License