Fix mutation name

src/plugins/vuex.ts

@@ -4,13 +4,13 @@ import { store } from '../store'
 
 export interface VuexAPIOptions {
   stateKey: 'instanceUrl' | string
-  mutation: 'instanceUrl' | string
+  mutation: 'instance/instanceUrl' | string
 }
 
 export const createVuexAPI = (vuexPluginOptions: Partial<VuexAPIOptions> = {}): Plugin<any> => (vuexStore) => {
   const options: VuexAPIOptions = {
     stateKey: 'instanceUrl',
-    mutation: 'instanceUrl',
+    mutation: 'instance/instanceUrl',
     ...vuexPluginOptions
   }