Copies `GraphIndexCreator.from_text()` to make an async version called
`GraphIndexCreator.afrom_text()`.
This is (should be) a trivial change: it just adds a copy of
`GraphIndexCreator.from_text()` which is async and awaits a call to
`chain.apredict()` instead of `chain.predict()`. There is no unit test
for GraphIndexCreator, and I did not create one, but this code works for
me locally.
@agola11 @hwchase17
Fixed a typo in the argument of the query method within the
VectorStoreIndexWrapper class. Specifically, the argument `retriver` has
been changed to `retriever`. With this correction, the correct argument
name is used, and potential bugs are avoided.
