move state into separate file as per vuex docs

app/assets/javascripts/projects/gke_cluster_dropdowns/store/index.js

@@ -3,6 +3,7 @@ import Vuex from 'vuex';
 import * as actions from './actions';
 import * as getters from './getters';
 import mutations from './mutations';
+import state from './state';
 
 Vue.use(Vuex);
 
@@ -10,15 +11,5 @@ export default new Vuex.Store({
   actions,
   getters,
   mutations,
-  state: {
-    selectedProject: {
-      projectId: '',
-      name: '',
-    },
-    selectedZone: '',
-    selectedMachineType: '',
-    projects: [],
-    zones: [],
-    machineTypes: [],
-  },
+  state,
 });

app/assets/javascripts/projects/gke_cluster_dropdowns/store/state.js

+export default {
+  selectedProject: {
+    projectId: '',
+    name: '',
+  },
+  selectedZone: '',
+  selectedMachineType: '',
+  projects: [],
+  zones: [],
+  machineTypes: [],
+};