add tests for sphinx=4.*

[Chilipp]

this PR adds the CI for sphinx 4.1-4.5 and python 3.9 and 3.10

[codecov]

Codecov Report

Merging #73 (48bad79) into master (979a51a) will decrease coverage by 2.49%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #73      +/-   ##
==========================================
- Coverage   86.68%   84.19%   -2.50%     
==========================================
  Files           1        1              
  Lines         308      310       +2     
==========================================
- Hits          267      261       -6     
- Misses         41       49       +8     

Impacted Files	Coverage Δ
autodocsumm/__init__.py	84.19% <0.00%> (-2.50%)	⬇️

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