Register a custom accepted content types contributor. A contributor function takes ApplicationCall
and a list of content types accepted according to HttpHeaders.Accept header or provided by the previous
contributor if exists. Result of this contributor should be a list of accepted content types
with quality. A contributor could either keep or replace input list of accepted content types depending
on use-case. For example a contributor taking
format=json request parameter could replace the original
content types list with the specified one from the uri argument.
Note that the returned list of accepted types will be sorted according to quality using sortedByQuality
so a custom contributor may keep it unsorted and should not rely on input list order.