Tempenv

- dropped python 3.7 and 3.8 (ci tests 3.9 through 3.13)
- updated dev and test dependencies (still no runtime dependencies)
- updated setup.py constructs

- convert to using ContextDecorator jeking3 in 22
- fixed incorrect type on initializer (value was not optional)
- dropped python 3.6 support (ci tests 3.7 through 3.10)
- update dev and test dependencies (still no runtime dependencies)

Changed

- Added PEP 561 compliant typing (and trove identifier)
- Added mypy in pre-commit and fixed one errant type.

Changed

- Move CI from Travis to GitHub
- Enable Dependabot

Added

- Added decorator support.

Changed

- Updated README with more examples.

Added

- Initial release.