Add vue-async-computed-decorator to README.md

[nwtgck]

Hi @foxbenjaminfox.

I think the decorator package, the like of vue-async-computed-decorator should be on README of this repository.

[foxbenjaminfox]

I agree, but for now I'm treating vue-async-computed-decorator as something of a beta release. I want to give it a few days or maybe a week or two to iron out all the details (such as this bug that just now got fixed), and after I'm sure that things are more or less stable I'll then release an official v1.0.0 of vue-async-computed-decorator and link to it from here.

[nwtgck]

@foxbenjaminfox Thanks. I understood the plan now. I'll use the decorator package first.