chore: Update readme for GraphQL spec compability

[calvincestari]

Trying to make it clearer for users to know which version of the GraphQL spec the client is compatible with.

[svc-apollo-docs]

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[changeset-bot]

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Latest commit: 2913fd8

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[calvincestari]

Keeping this as a draft until we've all agreed on the messaging.

[pkg-pr-new]

npm i https://pkg.pr.new/@apollo/client@12156

commit: 2913fd8

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[jerelmiller]

Feel free to merge when you're ready! Thanks for adding this.

[github-actions]

size-limit report 📦

Path	Size
dist/apollo-client.min.cjs	39.33 KB (0%)
import { ApolloClient, InMemoryCache, HttpLink } from "dist/main.cjs"	48.01 KB (0%)
import { ApolloClient, InMemoryCache, HttpLink } from "dist/main.cjs" (production)	45.59 KB (0%)
import { ApolloClient, InMemoryCache, HttpLink } from "dist/index.js"	34.4 KB (0%)
import { ApolloClient, InMemoryCache, HttpLink } from "dist/index.js" (production)	32.29 KB (0%)
import { ApolloProvider } from "dist/react/index.js"	1.26 KB (0%)
import { ApolloProvider } from "dist/react/index.js" (production)	1.24 KB (0%)
import { useQuery } from "dist/react/index.js"	5.21 KB (0%)
import { useQuery } from "dist/react/index.js" (production)	4.3 KB (0%)
import { useLazyQuery } from "dist/react/index.js"	5.69 KB (0%)
import { useLazyQuery } from "dist/react/index.js" (production)	4.77 KB (0%)
import { useMutation } from "dist/react/index.js"	3.62 KB (0%)
import { useMutation } from "dist/react/index.js" (production)	2.84 KB (0%)
import { useSubscription } from "dist/react/index.js"	4.42 KB (0%)
import { useSubscription } from "dist/react/index.js" (production)	3.48 KB (0%)
import { useSuspenseQuery } from "dist/react/index.js"	5.51 KB (0%)
import { useSuspenseQuery } from "dist/react/index.js" (production)	4.17 KB (0%)
import { useBackgroundQuery } from "dist/react/index.js"	5.01 KB (0%)
import { useBackgroundQuery } from "dist/react/index.js" (production)	3.66 KB (0%)
import { useLoadableQuery } from "dist/react/index.js"	5.09 KB (0%)
import { useLoadableQuery } from "dist/react/index.js" (production)	3.73 KB (0%)
import { useReadQuery } from "dist/react/index.js"	3.41 KB (0%)
import { useReadQuery } from "dist/react/index.js" (production)	3.35 KB (0%)
import { useFragment } from "dist/react/index.js"	2.28 KB (0%)
import { useFragment } from "dist/react/index.js" (production)	2.23 KB (0%)