Support default_lookup NestedFilteringFilterBackend

[michjk]

Is your feature request related to a problem? Please describe.
When I am using NestedFilteringFilterBackend, I just realize that it does not support "default_lookup" like FilteringFilterBackend.

Describe the solution you'd like
Support "default_lookup" like FilteringFilterBackend.

Describe alternatives you've considered
Do not have, but feel free to put workaround solution in this issue.

Additional context
Currently using django-elasticsearch-dsl-drf 0.22.5

[michjk]

Hi I am willing to work on this part. @barseghyanartur let me know if you have any issue.