UI: Add option for only one fullscreen projector per screen

This option is added for users who want to have only one
projector on a screen and want to save gpu resources.

UI/window-basic-main.cpp

@@ -8431,6 +8431,17 @@ OBSProjector *OBSBasic::OpenProjector(obs_source_t *source, int monitor,
 	if (monitor > 9 || monitor > QGuiApplication::screens().size() - 1)
 		return nullptr;
 
+	bool closeProjectors = config_get_bool(GetGlobalConfig(), "BasicWindow",
+					       "CloseExistingProjectors");
+
+	if (closeProjectors && monitor > -1) {
+		for (size_t i = projectors.size(); i > 0; i--) {
+			size_t idx = i - 1;
+			if (projectors[idx]->GetMonitor() == monitor)
+				DeleteProjector(projectors[idx]);
+		}
+	}
+
 	OBSProjector *projector =
 		new OBSProjector(nullptr, source, monitor, type);