ci: run checks and tests on PRs

[P403n1x87]

This PR ensures that checks and tests run on PRs

[codecov]

Codecov Report

Merging #122 (9e55b6d) into devel (d1e56c1) will decrease coverage by 0.17%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##            devel     #122      +/-   ##
==========================================
- Coverage   69.83%   69.66%   -0.18%     
==========================================
  Files          22       22              
  Lines        2347     2347              
  Branches      655      655              
==========================================
- Hits         1639     1635       -4     
- Misses        411      415       +4     
  Partials      297      297              

Impacted Files	Coverage Δ
src/py_string.h	70.51% <0.00%> (-3.85%)	⬇️
src/stack.h	82.01% <0.00%> (-1.44%)	⬇️
src/py_proc_list.c	74.80% <0.00%> (-0.77%)	⬇️
src/py_thread.c	72.72% <0.00%> (-0.65%)	⬇️
src/cache.c	88.06% <0.00%> (+2.84%)	⬆️

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