Add changeset

Author: jerelmiller

.changeset/fifty-books-return.md

@@ -0,0 +1,32 @@
+---
+"@apollo/client-graphql-codegen": minor
+---
+
+Introduce a new GraphQL Codegen plugin to generate the type policy configuration needed to configure custom scalars for each field.
+
+```ts
+// codegen.ts
+import type { ScalarTypePoliciesPluginConfig } from "@apollo/client-graphql-codegen/scalar-type-policies";
+
+const config: CodegenConfig = {
+  // ...
+  generates: {
+    "./path/to/schema-type-policies.ts": {
+      plugins: ["@apollo/client-graphql-codegen/scalar-type-policies"],
+      config: {
+        // ...
+      } satisfies ScalarTypePoliciesPluginConfig,
+    },
+  },
+};
+```
+
+This will generate a `scalarTypePolicies` object in the generated file that can be used to configure type policies.
+
+```ts
+import { scalarTypePolicies } from "./path/to/schema-type-policies";
+
+const cache = new InMemoryCache();
+
+cache.policies.addTypePolicies(scalarTypePolicies);
+```