cleanup code & update dependencies

[obfusk]

• use indent 4
• add type annotations
• modernise code & style
• flake8
• pylint
• mypy --strict --disallow-any-unimported

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• update dependencies
  • make compatible with latest flask/werkzeug #159
  • CI: update actions #150
  • jmdict etc. update JMDict/KanjiDic regularly #27
  • supported python versions
  • p4a & android (targetsdk etc., other apps too)
  • jquery etc.
  • use dependabot?
• kanjidraw too cleanup code etc. kanjidraw#22

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• remove/replace badges #160
• make tests pass w/o non-free data too #161
• accessibility https://github.com/obfusk/jiten/tree/a11y accessibility: assess & improve #40
• other open issues
  • stop supporting python 3.5 and use newer features when ubuntu xenial is EOL #107
  • don't use deprecated click.get_terminal_size() etc. #134
  • improve test coverage (missing recent features) #148
  • DB: jmdict entry.freq is not an integer (nor is it used) #155