fix: :sparkles: Add `cumulative gaussian` (#611)
* fix: :sparkles: Add `cumulative gaussian`
* test: :recycle: Add and refactore `models` and `tests`
* fix: :test_tube: Fixed wrong assert comparsion
* fix: :memo: Correct links
* Correct links in `mkdocs` to `code`
* fix: :arrow_up: increase back coverage rate
* fix: :zap: finished review
