Updates packages to recent version

[maroskukan]

This patch resolves #12 as well as updates remaining packages.

The following workflow was done:

pip3 list --format=freeze | grep -v '^\-e' | cut -d = -f 1 | xargs -n1 pip3 install -U
pip3 freeze > requirements.txt

One exception is charset-normalizer which needs to stay at 2.1.1 and not latest 3.0.1 because of aiohttp 3.8.3 dependency.

It also fixes warning with Flask

'FLASK_ENV' is deprecated and will not be used in Flask 2.3. Use 'FLASK_DEBUG' instead.