Update documentation to cover testing using pytest

[slidenerd]

Please add a section in your documentation on how to test code that uses pool, fetch, executemany etc using pytest. I could not find anything on stackoverflow or issues where is a slight reference somewhere to TempCluster but no examples whatsoever. Are you supposed to mock this library or create an actual database while testing. Would be super helpful for future readers

[Coinhexa]

@slidenerd is referring to THIS COMMENT I think but your documentation has no mention of this anywhere on how to setup tests/temporary instance with a TempCluster. Super appreciate if you can update your documentation with this