Static Site Editor: Ordered lists shouldn’t increment automatically

What does this MR do?

It modifies Toast UI’s HTML to Markdown converter to allow specifying ordered lists are incrementable or not when generating Markdown from the WYSIWYG editor. By default, ordered lists are not incrementable Handbook Markdown guide, for example:

1. list item 1
1. list item 2
1. list item 3

How to test?

Open a markdown document in the Static Site Editor. In your local environment, you can open http://127.0.0.1:3000/h5bp/html5-boilerplate/-/sse/master%2FREADME.md. Add an ordered list in the WYSIWYG mode:

When switching from WYSIWYG mode to Markdown mode or saving the changes, you should see that the ordered list does not have incremental numbers.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team