Add a py.typed file to the template

[paddyroddy]

Is Your Feature Request Related to a Problem? Please Describe

We are encouraging typing through the use of mypy already, it makes sense that we include the file by default https://safjan.com/the-importance-of-adding-py-typed-file-to-your-typed-package

Describe the Solution You'd Like

Add a py.typed file

Describe Alternatives You've Considered

No response

Additional Context

No response