Add changeset

Author: jerelmiller

.changeset/witty-llamas-drum.md

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+"@apollo/client": major
+---
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+Add a new `dataState` property to `ApolloQueryResult` that determines whether the `data` property is a complete result or not. As such, the `ApolloQueryResult` type is now a discriminated union that better handles the type of `data` given its particular state. The values are:
+
+- `none`: No data could be fulfilled from the cache or the result is incomplete. `data` is `undefined`.
+- `partial`: Some data could be fulfilled from the cache but `data` is incomplete. This is only possible when `returnPartialData` is `true`.
+- `hasNext`: `data` is incomplete as a result of a deferred query and the result is still streaming in.
+- `complete`: `data` is a fully satisfied query result fulfilled either from the cache or network.