Add tabbed changeform support (#211).

* WIP : basic templates

* Add params

* Working override

* Use headerless version only during tabs

* Move CSS to separate file

* Extract js to static folder

* script is not self-closing

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* use classList for updating classes

* Add EOF (newline) to new text files

* a simple test to keep up code coverage

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Fieldsets are not tabbed by default

* rename templatetag

* use default page if show_*_tabs are false

* Narrow down css to admin-interface

* Fix typo

* keep codacy happy

* prefix tab classes with tabbed-changeform-

* horizontal scrolling

* Update colors

* color updates

* add back missing font bold

Co-authored-by: vaz <vmohan@lenbox.io>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

tests/test_templatetags.py

@@ -168,3 +168,9 @@ class AdminInterfaceTemplateTagsTestCase(TestCase):
             "{{ version_md5_hash }}"
         )
         self.assertEqual(rendered, hash_manual)
+
+    def test_get_admin_interface_inline_template(self):
+        headless_template = templatetags.get_admin_interface_inline_template(
+            "admin/edit_inline/stacked.html"
+        )
+        self.assertEqual(headless_template, "admin/edit_inline/headerless_stacked.html")