[Readme] add info on how to build and run the tests

[jordalgo]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (7c88a61) 13.49% compared to head (dfdf6a9) 13.02%.
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #29      +/-   ##
==========================================
- Coverage   13.49%   13.02%   -0.47%     
==========================================
  Files          33       34       +1     
  Lines        2283     2364      +81     
==========================================
  Hits          308      308              
- Misses       1975     2056      +81     

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[qdeslandes]

I think it would be simpler if you update the first code snippet, like:

Quick start:

cmake -S . -B build
# Build bpfilter and libbpfilter
make -C build -j
# Run unit tests
make -C build test

[jordalgo]

Updated.