[upstream] [GHS] Allowing `<ul type>` or `<ol type>` in SourceEditing crashes CKEditor 5 when editing `<ul></ul>` or `<ol></ol>` without any <li> elements as children

Problem/Motivation

Existing sites with CKEditor 4 can have 'Allowed HTML tags' containing the tags
<ul type> <ol type start>

For example:

When switching to CKEditor 5, these tags will be added to "Manually editable HTML tags":

Issue #3261599: Use CKEditor 5's native <ol start> support (and also support <ol reversed>) already covers 'start'.
However, 'type' is not yet handled and causes CKEditor 5 to break when empty lists are present, or added, using the Source option.

Steps to reproduce

The easiest way to trigger the same behaviour :

1. Configure CKEditor 5 with the "Manually editable HTML tags" to include <ul type> <ol type>
2. Configure CKEditor 5 to include the "Source" button in the toolbar
3. Find/create a text field on content using the editor and prepare it wil a list with at least one list item.
4. Switch to "Source" mode and add an empty list (ul, ol) to the field.
5. Turn off "Source" mode and observe CKEditor throwing an error while nothing visually happens.
6. Try to turn off "Source" mode again a few times and observe weird visual behaviour

Example:

https://www.drupal.org/files/issues/2022-04-08/ckeditor5.mov

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet