Update documentation stack / tox.ini for building documentation

[dweindl]

• Update exhale, sphinx, ... to fix some incompatibilities
• Set up tox.ini for building documentation

[codecov]

Codecov Report

Merging #2213 (ab78ad6) into develop (664994c) will decrease coverage by 22.74%.
Report is 1 commits behind head on develop.
The diff coverage is 78.45%.

❗ Current head ab78ad6 differs from pull request most recent head f418276. Consider uploading reports for the commit f418276 to get more accurate results

Additional details and impacted files

@@             Coverage Diff              @@
##           develop    #2213       +/-   ##
============================================
- Coverage    76.51%   53.77%   -22.74%     
============================================
  Files           86       43       -43     
  Lines        15025     5668     -9357     
============================================
- Hits         11496     3048     -8448     
+ Misses        3529     2620      -909     

Flag	Coverage Δ
cpp	?
cpp_python	?
petab	53.77% <78.45%> (+0.02%)	⬆️
python	?
sbmlsuite	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
python/sdist/amici/__main__.py	0.00% <ø> (ø)
python/sdist/amici/petab/cli/import_petab.py	0.00% <ø> (ø)
python/sdist/amici/petab/simulator.py	100.00% <100.00%> (ø)
python/sdist/amici/petab_util.py	0.00% <ø> (ø)
python/tests/test_petab_import.py	100.00% <100.00%> (ø)
python/tests/test_petab_objective.py	100.00% <ø> (ø)
python/tests/test_petab_simulate.py	100.00% <ø> (ø)
python/sdist/amici/parameter_mapping.py	0.00% <0.00%> (ø)
python/sdist/amici/petab_objective.py	0.00% <0.00%> (-92.71%)	⬇️
python/sdist/amici/petab_simulate.py	0.00% <0.00%> (-100.00%)	⬇️
... and 5 more

... and 65 files with indirect coverage changes

[FFroehlich]

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