Add commands to toggle visibility of manager and custom nodes manager menus (#1505)

* Add commands for manager keybindings

* use more consistent isVisible condition check

* remove hide method in favor of super class's close method

* fix formatting

* fix tabs formatting

js/custom-nodes-manager.js

@@ -1916,4 +1916,8 @@ export class CustomNodesManager {
 	close() {
 		this.element.style.display = "none";
 	}
+
+	get isVisible() {
+		return this.element?.style?.display !== "none";
+	}
 }