a big --fix indeed

Update functional_programming/05_functors.py

fix(functors): remove custom css link

refactor(functors): `v0.1.5` of `functors.py`

fix(functors): remove custom theme link

refactor(functors): `v0.1.4` of notebook `functors` for fp course

refactor(functors): `v0.1.3` of `functors` notebook

refactor(functor): migrate to python3.13

refactor(fp): v0.1.1 of notebook 05_functors.py

Fixing typo

Improve notebook and README as suggested by Haleshot

Add notebook 05_functors (version 0.1.0) for the functional programming course

Remove duplicate implementations in markdown

Demo version of 05_functors.py