* Add docs for histogram
* Add docs and make changes:
- Made changes suggested in first review
- Add docs for relevant files
* Rename docs file and correct typos
* Change doc for cumulative histogram
* Add docs for histogram equalization
* Make changes suggested in review
* Add docs
* Remove docs for algorithms
* Move images to test_images
Co-authored-by: Mateusz Łoskot <mateusz@loskot.net>
