fix(vue): extends ComponentOptions with ability member (#73)

Allows:

```ts
import { abilitiesPlugin } from '@casl/vue'
import Vue from 'vue';
import ability from './ability'

new Vue({
  router,
  store,
  ability,
  render: (h) => h(App),
}).$mount('#app')
```

packages/casl-vue/index.d.ts

@@ -9,3 +9,9 @@ declare module "vue/types/vue" {
     $can(action: string, subject: any, field?: string): boolean
   }
 }
+
+declare module "vue/types/options" {
+  interface ComponentOptions<V extends Vue> {
+    ability?: Ability;
+  }
+}