Use towncrier for newsfragment/changelog management

[fizyk]

• Add towncrier configuration (based of off pytest-redis for example)
• Add towncrier to pipenv's Pipfile (will be first file initialisation)
• Add github-action that'll check pr's for the newsfragment file: https://github.com/ClearcodeHQ/pytest-redis/blob/main/.github/workflows/pr-check.yml
• CHange pr template to https://github.com/ClearcodeHQ/pytest-redis/blob/main/.github/PULL_REQUEST_TEMPLATE.rst
• recreate newsfragments for changes since last release