fix(docs): grpc docs (#852)

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#### Migration notes

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- [ ] The change comes with new or modified tests
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docs/metatype.dev/docs/reference/runtimes/grpc/grpc.graphql

@@ -0,0 +1,5 @@
+query {
+  greet(name: "Metatype") {
+    message
+  }
+}

docs/metatype.dev/docs/reference/runtimes/grpc/index.mdx

@@ -35,4 +35,5 @@ This method creates a typegraph function for gRPC method calls. It accepts the f
   typegraph="grpc"
   typescript={require("!!code-loader!../../../../../../examples/typegraphs/grpc.ts")}
   python={require("!!code-loader!../../../../../../examples/typegraphs/grpc.py")}
+  query={require("./grpc.graphql")}
 />