Hotfix type hinting syntax for python 3.8 compatibility
What's Changed
* update setup.py, __init__.py by wen-jams in https://github.com/wen-jams/inviz/pull/69
* fix type hinting for py3.8 compatibility by wen-jams in https://github.com/wen-jams/inviz/pull/70
**Full Changelog**: https://github.com/wen-jams/inviz/compare/v0.2.3...v0.2.4