Fix linting errors in speech module

[nathonfowlie]

• Fixed linting issues found by flake8, pylint and black in the speech module.
• Fixed some missing type hints, but didn't resolve all issues found by mypy.

refs:

• relates to #17

[nathonfowlie]

The PR check seems to be failing because there's a white-space character in the credentials passed through to auth.py

https://stackoverflow.com/questions/74145180/praw-invalid-leading-whitespace-reserved-characters-or-returncharacters-i