Test correct :params in splitdef on constructor

[kunzaatko]

When looking at the documentation, I did not immediately realize that :params are used in constructors. I added a note
about that for users with the same question.
While exploring the package, I noticed that there is not test of correct :params detection on splitdef so I added
one.

Summary:

• Added a note to the documentation on the purpose of params
• Added a test to check that the detection of :params works in splitdef

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.68%. Comparing base (c9f9e98) to head (0aa6143).
Report is 19 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #211      +/-   ##
==========================================
- Coverage   79.48%   78.68%   -0.81%     
==========================================
  Files          10        9       -1     
  Lines         429      441      +12     
==========================================
+ Hits          341      347       +6     
- Misses         88       94       +6     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[cstjean]

Thanks!