Re-add __main__.py to enable executing as a module

[michaeltinsley]

Description

Re-adds __main__.py to enable executing as a module.
This was added in 0.12.6, and removed in 1.7.3.

Related Issue

Closes #496

Motivation and Context

With this, prospector paths don't need to be added.
In my experience, it also make integration with CI easier.

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• My change requires a change to the dependencies
• I have updated the dependencies accordingly
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[carlio]

Thanks! 👍

[michaeltinsley]

Thanks for the speedy turnaround, made my life a lot easier 👍

[carlio]

No worries, I'll make a small bugfix release tomorrow (it is a bug to me - something was working and now it's not!) - and thanks for the PR

[carlio]

1.7.7 on PyPI now