Add/Move helpers to register OBS websocket vendor requests

Adds websocket vendor requests to start and stop the plugin.
Adds vendor events to indicate when the plugin is started or stopped.

These are ntended to be used for the StreamDeck plugin support.

lib/advanced-scene-switcher.cpp

@@ -14,6 +14,7 @@
 #include "tab-helpers.hpp"
 #include "utility.hpp"
 #include "version.h"
+#include "websocket-api.hpp"
 
 #include <obs-frontend-api.h>
 #include <QAction>
@@ -454,6 +455,8 @@ void SwitcherData::Start()
 
 		// Will be overwritten quickly but might be useful
 		writeToStatusFile("Advanced Scene Switcher running");
+		SendWebsocketVendorEvent("AdvancedSceneSwitcherStarted",
+					 nullptr);
 	}
 
 	if (showSystemTrayNotifications) {
@@ -481,6 +484,10 @@ void SwitcherData::Stop()
 		delete th;
 		th = nullptr;
 		writeToStatusFile("Advanced Scene Switcher stopped");
+		if (!obsIsShuttingDown) {
+			SendWebsocketVendorEvent("AdvancedSceneSwitcherStopped",
+						 nullptr);
+		}
 	}
 
 	if (showSystemTrayNotifications) {