How to create a filter from start to finish

[mariajgrimaldi]

Description

Some comments I've gathered from the community survey on the challenges/suggestions section:

I would only improve the documentation a little bit. For example, in the section on creating a filter it talks about two different filters, which may cause confusion. I think it would be good to show an example of a filter implemented from start to finish, which contains all or at least most of the functionality offered by the library. additionally, the openedx-filters-samples repository has a great variety of examples, but it shows the filter creation part, but not (I think) the filter usage which is also important.