I am developing a VSCode extension with a CustomEditor for editing HTML.

The target files are only HTML files, and when the file is opened, the default text editor is displayed. From that state, it is possible to open the CustomEditor.

When I open the WebView of the CustomEditor, breadcrumbs containing only the file name are displayed at the top, as shown in the image below.

I would like to change the content displayed in these breadcrumbs.
How can I do this?