Add RouterLink event on click

[marsimeau]

Linked to vuejs/vue-router#800.

What problem does this feature solve?

In vue 2 we could add v-on:click.native="myClickHandler" on RouterLink to listen for clicks on the link element. This is no longer possible since the .native modifier has been removed. Since using the @click event currently breaks the link, adding a click event or an equivalent would allow us to replicate that simple pattern without having to wrap the link which is unconventional or having to customize it with the custom prop which is much more verbose.

What does the proposed API look like?

Emit a click event:

<router-link to="/my-route" @click="myClickHandler">My link</router-link>

Or emit a navigate event, if click isn't considered the right event for this.

<router-link to="/my-route" @navigate="myNavigateHandler">My link</router-link>

[posva]

Duplicate of #846