Add hook for filtering selected filters in Facets.php

[burhandodhy]

Description of the Change

This PR adds a new filter in the get_selected method

Closes #

How to test the Change

Changelog Entry

Added - Introduce a new filter ep_facet_selected_filters

Credits

Props @burhandodhy

Checklist:

• [x] I agree to follow this project's Code of Conduct.
• [x] I have updated the documentation accordingly.
• [ ] I have added tests to cover my change.
• [x] All new and existing tests pass.