How use lozad with nuxt (vue) ?

I installed lozad by npm.

I created plugin lozad.js.

```
import Vue from 'vue';
import lozad from 'lozad';

let observer = lozad('.lozad', {
threshold: 0
});

Object.defineProperty(Vue.prototype, '$lozad', { value: observer });
```

In container mounted lifecycle called function:

```
mounted() {
this.$lozad.observe();
```

I want use lozad with picture tag.

```





```

Why my placeholder image from img tag did not load, instead, the image from the first source.