Add support for Python 3.9

[hugovk]

No description provided.

[codecov]

Codecov Report

Merging #38 into master will decrease coverage by 11.69%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master      #38       +/-   ##
===========================================
- Coverage   55.99%   44.29%   -11.70%     
===========================================
  Files           5       12        +7     
  Lines         434     1727     +1293     
===========================================
+ Hits          243      765      +522     
- Misses        191      962      +771     

Flag	Coverage Δ
#GHA_Ubuntu_16	44.97% <ø> (-10.33%)	⬇️
#GHA_Ubuntu_18	44.97% <ø> (-10.33%)	⬇️
#GHA_Ubuntu_20	44.97% <ø> (?)
#GHA_macOS	46.33% <ø> (-8.97%)	⬇️

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Impacted Files	Coverage Δ
test/functional/test_manager.py	100.00% <ø> (ø)
...py/lib/python3.8/site-packages/osmviz/animation.py	0.00% <0.00%> (ø)
...py/lib/python3.6/site-packages/osmviz/animation.py	0.00% <0.00%> (ø)
...py/lib/python3.9/site-packages/osmviz/animation.py	0.00% <0.00%> (ø)
...x/py/lib/python3.6/site-packages/osmviz/manager.py	79.87% <0.00%> (ø)
...py/lib/python3.7/site-packages/osmviz/animation.py	0.00% <0.00%> (ø)
...x/py/lib/python3.8/site-packages/osmviz/manager.py	79.87% <0.00%> (ø)
...x/py/lib/python3.9/site-packages/osmviz/manager.py	79.87% <0.00%> (ø)
...x/py/lib/python3.7/site-packages/osmviz/manager.py	79.87% <0.00%> (ø)

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