Improve documentation of Singleton functions, change to createInstance (#2585)

Signed-off-by: Sebastian Malton <sebastian@malton.name>

src/renderer/utils/__tests__/storageHelper.test.ts

@@ -5,7 +5,7 @@ import { ClusterStore } from "../../../common/cluster-store";
 
 describe("renderer/utils/StorageHelper", () => {
   beforeEach(() => {
-    ClusterStore.getInstanceOrCreate();
+    ClusterStore.createInstance();
   });
 
   afterEach(() => {