* Add rail fence cipher encoder & decoder
* Add functions to encode & decode strings using the rail fence cipher method
* Add unit tests covering empty strings, pair & odd number of characters in the input string, n=3 & n=4
* Add a README.md for the algorithm
* Update root README.md to link to the new algorithm
* Rename the CI workflow file.
Co-authored-by: Oleksii Trekhleb <trehleb@gmail.com>
