Wagtail-autocomplete

* Change the search view to use the HTTP POST method, which can prevent the request URI from becoming too long.
* New feature: add the possibility of a custom filter function.

* Add Wagtail 3.x compatibility

- Change in behavior: the autocomplete endpoint will return a 404 response if no objects are found.
- Update Javascript dependencies to remove security vulnerabilities

- **Breaking change**: Drop deprecated `page_type` and `is_single` arguments from `AutocompletePanel`
- Update the panel and widget codes based on panels of `wagtail.admin.edit_handlers` - mainly `PageChooserPanel`
- Security updates of NPM dependencies
- Update use of deprecated `django.conf.urls.url` function.

* Remove native browser autocomplete from field