Add unit tests + docs for Distributions.Discrete.Bernoulli

[Freymaurer]

Please reference the issue(s) this PR is related to

Closes #211

Please list the changes introduced in this PR

• 1 testList "Distributions.Discrete.Bernoulli" with 7 tests ✅
  • testing bernCheckParam for edge case coverage
  • test all member functions of Distributions.Discrete.Bernoulli used in Distributions.Discrete.bernoulli
  • do all tests on different bernoulli distributions covering: min, max, default and nan.
• fix bug in PDF calculation 🐛
• fix bug in CDF calculation 🐛
• add docs 📚

[Required] please make sure you checked that

• [x] The project builds without problems on your machine

[Optional]

• [x] Added unit tests regarding the added features