reduce typos in README.md

Problem/Motivation

As a new user of the module, I find the inconsistencies in the README confusing.

Steps to reproduce

• The file specifies that the namespace should be Drupal\Hooks\MyModuleHooks but then the example shows Drupal\my_module\Hooks, the latter of which I believe is correct.
• The final example function is named myEntityAccess() and returns an AccessResult even though it is not acting on access hooks and does not have the necessary parameters to be an access hook, and even though that function name was already used earlier in the example file.

Proposed resolution

Someone who knows how the module works and can confirm that these are errors, please correct the documentation so the rest of us can be less confused. Thank you!