Unity: ignore TextMesh Pro (#2988)

Unity.gitignore

@@ -11,6 +11,9 @@
 # Uncomment this line if you wish to ignore the asset store tools plugin
 # [Aa]ssets/AssetStoreTools*
 
+# TextMesh Pro files
+[Aa]ssets/TextMesh*Pro/
+
 # Visual Studio cache directory
 .vs/