Merge branch '3.4' into 4.4

* 3.4:
  👽 Updated links to Bootstrap docs

Author: OskarStark

form/bootstrap4.rst

@@ -12,10 +12,10 @@ template which other templates extend from):
 
     {# beware that the blocks in your template may be named different #}
     {% block head_css %}
-        <!-- Copy CSS from https://getbootstrap.com/docs/4.1/getting-started/introduction/#css -->
+        <!-- Copy CSS from https://getbootstrap.com/docs/4.4/getting-started/introduction/#css -->
     {% endblock %}
     {% block head_js %}
-        <!-- Copy JavaScript from https://getbootstrap.com/docs/4.1/getting-started/introduction/#js -->
+        <!-- Copy JavaScript from https://getbootstrap.com/docs/4.4/getting-started/introduction/#js -->
     {% endblock %}
 
 If your application uses modern front-end practices, it's better to use
@@ -120,7 +120,7 @@ is a strong connection between the error and its ``<input>``, as required by the
 `WCAG 2.0 standard`_.
 
 .. _`WCAG 2.0 standard`: https://www.w3.org/TR/WCAG20/
-.. _`custom forms`: https://getbootstrap.com/docs/4.3/components/forms/#custom-forms
+.. _`custom forms`: https://getbootstrap.com/docs/4.4/components/forms/#custom-forms
 .. _`custom radio`: https://getbootstrap.com/docs/4.3/components/forms/#radios
 .. _`custom checkbox`: https://getbootstrap.com/docs/4.3/components/forms/#checkboxes
 .. _`switch instead of a checkbox`: https://getbootstrap.com/docs/4.3/components/forms/#switches