Imfp

- Updated dependencies

- Removed deprecated pkg_resources import

- Fixed a problem with pyproject.toml that was breaking CI/CD

- Implemented automated PyPi deployment with GitHub Actions

- Implemented response mocking during unit tests

- Removed between-calls wait time during unit tests

- Changed wait time variable from a global variable to an environment variable

- Introduced new `set_imf_wait_time` function

- Handled a case where, apparently, certain databases have required request parameters

- Added a couple experimental scripts for users who want to download whole databases; use at your own risk (of being blocked by the API)!

- Added error handling for the case where the user-specified parameter codes are valid, but the years are outside the dataset's range

- Adjusted the regular expression used in passing through error messages from the API endpoint

- Corrected bug in URL handling when user omits one or more parameters

- Improved error handling to prevent confusing JSON decode errors from being passed to user

- Implemented formatting with `black` library

- Minor adjustments to project docs

- Linted unit tests