thisall

const app = createApp({
    render: () => (
        h(App)
    ),
    methods: {
        ...mapMutations([
            'showLoading',
        ]),

        ...mapActions([
            'addNotification',
        ]),
    },
});

app.use(router);
app.use(store);
app.mount('#app')

<button class="btn-more" data-site="<?=$post_id++?>">подробнее</button>