All: Added "None" sync target to allow disabling synchronisation

packages/lib/SyncTargetNone.ts

@@ -0,0 +1,30 @@
+import { _ } from './locale.js';
+import BaseSyncTarget from './BaseSyncTarget';
+import { FileApi } from './file-api';
+
+export default class SyncTargetNone extends BaseSyncTarget {
+
+	public static id() {
+		return 0;
+	}
+
+	public static targetName() {
+		return 'none';
+	}
+
+	public static label() {
+		return _('(None)');
+	}
+
+	public async fileApi(): Promise<FileApi> {
+		return null;
+	}
+
+	protected async initFileApi() {
+
+	}
+
+	protected async initSynchronizer() {
+		return null as any;
+	}
+}