more documentation about way to add functions

[Royal-Duck]

There is absolutely no documentation about the way to add functions and the code base is going everywhere

I'd like to be able to add new functions to the calculation app toolbox

Describe the solution you'd like

I'd like a markdown file in the docs folder that explains just that

Additional context

I want this as I originally wanted to do a difference of binomcdf and to implement it as a function like a ranged distributive function

[adri1numworks]

Hello, it is planned internally. We just have to find the time to do this... i'll keep you updated!