Azure DevOps Server 2019 extension: How do I limit the work item data entry forms my custom page appears on?

Question

I'm using Azure Devops Server 2019, update 1.1. My goal is to write an extension that presents a new page, but only on the user story work item data entry form and not the data entry form for a Task, Bug, Issues, etc. See screen shot

Here is the contributions section of my vss-extension.json (It's what produced the custom page in the screen shot above). I've read Extension manifest reference, but I can't find a setting related to limiting which form a new page appears on.

Does anyone know which area of the extensions architecture I need to work in to limit which forms on which a new page appears?

"contributions": [
    {  
        "id": "sample-work-item-form-page",
        "type": "ms.vss-work-web.work-item-form-page",
        "description": "Custom work item form page",
        "targets": [
            "ms.vss-work-web.work-item-form"
        ],
        "properties": {
            "name": "Create Standard Tasks",
            "uri": "workItemPage.html"
        } 
    }
]

Answer 1

By reference to this doc: Extend the work item form, this web extension belongs to Azure Boards service, so it will appear in all work item pages as your mentioned doc: Extension manifest reference. Currently it is not documented to specify which work item type it appears in.

In addition, you could directly follow this doc: Customize the web layout for a work item type (Inheritance process) to add a custom page to the user story work item.