Nshm-toshi-client

Changes
- added requests and aiohttp extras to gql dependency
- update poetry config
- apply formatting / linter rules
- remove twine from setup
- update mkdocs config

Added
- ToshiFile.download_file function
- doco for env variables
Changes
- update usage.md with download_file instruction usage
- File.file_size from Int to BigInt

Changes
- disabled schema validation (for now?)

Added
- get_file method to ToshiFile class
- tests for get_file method
- update usage.md

Changes
- using poetry in place of setup.py.

Added
- [Docs](https://gns-science.github.io/nshm-toshi-client) in /docs are published (mkdocs)
- CHANGELOG.md and version management using `poetry run bump2version major|minor|patch`
- CONTRIBUTING.md
- testing pytest
- coverage via pytest-cov
- linting with flake8 (although very limited right now)
- formatting with black
- GH workflows:
- test matrix in tox covering [Windows, Posix, Macos] * [py38 ,py3.9]
- publish coverage
- publish package to test.pypi.org and pypi.org

Changes
- Don't set logging level.