Content not showing up in custom Dialog box

[AnuragVinodh]

Hello, I am currently trying to make an azure devops extension that shows a list of sub tickets for a given work item in a custom dialog box.

This is my contributions in the manifest json:

and this would be my code :

The .addItemsDialog extension points to a html page:

When I publish my code, all I see is this:

No content gets displayed on the custom dialog box. What might have I done wrong here? I have followed the example in hub.tsx. I would like to replace the html page with a simple react app at some point.