Add Visual Studio Code cache directory

Since a long time, developers have been able to use Visual Studio Code inside of Unity. I don't claim exactly to know how it works, but regardless its cache directory should be ignored, whether it is ever created or not (if not now, it might be in the future).

Unity.gitignore

@@ -26,6 +26,9 @@
 # Visual Studio cache directory
 .vs/
 
+# Visual Studio Code cache directory
+.vscode/
+
 # Gradle cache directory
 .gradle/