feat: Make add() accept args funcs

[codecov[bot]]

Codecov Report

Merging #230 (dd6c4a2) into master (0cb465d) will increase coverage by 4.45%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #230      +/-   ##
==========================================
+ Coverage   90.53%   94.98%   +4.45%     
==========================================
  Files           5        5              
  Lines         338      339       +1     
==========================================
+ Hits          306      322      +16     
+ Misses         32       17      -15     

Impacted Files	Coverage Δ
...ometheus_fastapi_instrumentator/instrumentation.py	97.10% <100.00%> (+0.04%)	:arrow_up:
src/prometheus_fastapi_instrumentator/metrics.py	93.70% <0.00%> (+10.48%)	:arrow_up:

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.