Implement CloseDialogCommand in htmx

Problem/Motivation

Document how to implement CloseDialogCommand using htmx

Proposed resolution

Document at https://www.drupal.org/docs/develop/drupal-apis/htmx/ajax-api-to-htmx/closedialogcommand

Remaining tasks

1. Decide if and where we should re-implement core/misc/dialog/dialog.js without jQuery.
2. If dialog.js needs refactoring for use with htmx, open or link an issue for that work.
3. Edit linked page and add documentation

User interface changes

None

Introduced terminology

None

API changes

None

Data model changes

None

Release notes snippet

None