[FR] Optionally display custom fields in product backlog

[stxm]

Please describe the problem / need you are trying to solve. The values of user stories custom fields enhance the overview can be useful for sorting stories.

Describe the feature or the improvement you'd like and what are you trying to achieve. Optionally allow user stories custom fields to be used as columns within the backlog view. Furthermore, sorting would be the value of the column would be a great addition.

Describe alternatives you've considered n/a Additional context n/a