fix(docs): Update AppSync operations to a Lambda layer

[VamOSGS]

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Description of changes: Updated AppSync operations to a Lambda layer example snippet when we get response from https.request it will be large when first time 'data' event will be fired and argument ``` data `` will be not full response, it will be just chunk of response, so I updated that snippet and now by this PR: on data event it we will add chunk to response and only on 'end' we will parse and resolve Promise

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