feat: adding retry mechanism and unit test

[danyloB]

Implemented following functionality:

• if the retry option is on, network errors are retried immediately
• if the retry option is on, 429 status codes are retried after the delay specified by the Retry-After header in the response
• if the retry option is on, GraphQL requests are retried after the cost is likely to be available in the rate limit again
• shopify-api-node's automatic rate limit avoidance (autoRetries) should still work if the retry option is on
• the library should not retry indefinitely, and give up after some number of retries, throwing an error to the caller
• all code needs to be tested