[feat] Add asyncData Method Type to ComponentOptions Module Augmentation

[ryanmillerdev]

We use Vue SSR heavily at @algorithmiaio, and we've followed the Vue SSR-sanctioned means of declaring async data methods. We've shimmed together our own module augmentation for the asyncData method, but given the prevalence of asyncData usage throughout the Vue community, it would be nice to standardize the interface.

I was torn as per where this should live - there isn't a repo for SSR, given that it lives in the Vue repo, and ultimately it felt right here with the Vuex project, since asyncData and Vuex go hand in hand.

I've added a test for the new type as well, and let me know if there's anything I can tweak. Cheers!

[ktsn]

Thanks for contribution. However this change is not appropriate for Vuex since asyncData is not a part of Vuex API. Also the asyncData implementation can be different among implementations and they can conflict if we have this type in Vuex. For example, Nuxt.js asyncData has its own context type.

Maybe, It should be stated how to augment asyncData type in the SSR docs.

[ryanmillerdev]

Good call - thanks for taking a look!

[ktsn]

I just opened an issue on SSR docs vuejs/vue2-ssr-docs#174