Allow rendering custom widgets from root templates dir (#2356)

* Allow rendering custom widgets from root templates dir

Rendering custom widgets from the projects root template directory
doesn't work out of the box.

See: https://stackoverflow.com/questions/45844032/django-templatedoesnotexist-in-case-of-a-custom-widget/46208414#46-208414

This changes the setting to use the same template finding logic that the
TEMPLATES setting uses.

* update APP_DIRS=True

* fixup! update APP_DIRS=True

{{cookiecutter.project_slug}}/config/settings/base.py

@@ -68,6 +68,7 @@ DJANGO_APPS = [
     "django.contrib.staticfiles",
     # "django.contrib.humanize", # Handy template tags
     "django.contrib.admin",
+    "django.forms",
 ]
 THIRD_PARTY_APPS = [
     "crispy_forms",
@@ -196,6 +197,10 @@ TEMPLATES = [
         },
     }
 ]
+
+# https://docs.djangoproject.com/en/dev/ref/settings/#form-renderer
+FORM_RENDERER = "django.forms.renderers.TemplatesSetting"
+
 # http://django-crispy-forms.readthedocs.io/en/latest/install.html#template-packs
 CRISPY_TEMPLATE_PACK = "bootstrap4"