Drop Python 3.8

[kytta]

• Bump Python version
• Rewrite source
• Remove 3.8 from Hatch matrix
• Remove 3.8 from GitHub Actions

[codecov]

Codecov Report

Merging #43 (74ace0f) into main (58ea564) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 74ace0f differs from pull request most recent head f0bdc5d. Consider uploading reports for the commit f0bdc5d to get more accurate results

@@            Coverage Diff            @@
##              main       #43   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         2           
  Lines          101        99    -2     
  Branches        22        22           
=========================================
- Hits           101        99    -2     

Files Changed	Coverage Δ
skyr.py	100.00% <100.00%> (ø)
tests/skyr_test.py	100.00% <100.00%> (ø)