Better document how to create a custom filter

[pozylon]

It's not quite clear what the advantages of unchained's filter system for products and categories are and where the limitations of ORM based graphql tooling lie.

[pozylon]

Pro / Con about ORM's and the potential performance implications it could have on Unchained vs. further optimizing the existing code to be as near to the metal as possible.

https://medium.com/@mithunsasidharan/should-i-or-should-i-not-use-orm-4c3742a639ce
https://seldo.com/posts/orm_is_an_antipattern
http://webcache.googleusercontent.com/search?q=cache:I5zDVSbY_YYJ:https://martinfowler.com/bliki/OrmHate.html&client=safari&hl=de&gl=ch&strip=1&vwsrc=0

[pozylon]

postponed because we need docusaurus first