[Excel PowerPoint] (content addins) add support for unified manifest

docs/design/content-add-ins.md

@@ -1,7 +1,7 @@
 ---
 title: Content Office Add-ins
 description: Content add-ins are surfaces that can be embedded directly into Excel or PowerPoint documents that give users access to interface controls that run code to modify documents or display data from a data source.
-ms.date: 06/27/2024
+ms.date: 09/26/2024
 ms.topic: overview
 ms.localizationpriority: medium
 ---
@@ -41,11 +41,46 @@ For Mac, the personality menu measures 26x26 pixels, but floats 8 pixels in from
 
 ## Implementation
 
-There are minor differences in the manifests between content add-ins and add-ins that use task panes.
+There are minor differences in the manifests between content add-ins and add-ins that use task panes. Open the tab for the type of manifest you're using.
+
+# [Unified manifest for Microsoft 365](#tab/jsonmanifest)
+
+> [!NOTE]
+> The unified manifest is available in Excel, PowerPoint, and Word as a developer preview. For Outlook, it's generally available and can be used in production add-ins. 
+
+Configure the manifest with the following steps.
+
+1. Add a "contentRuntimes" child array to the extension object in the "extensions" array.
+1. Remove the "runtimes" property if it is present. The "runtimes" array is for task pane or mail add-ins. These cannot be combined with a content add-in.
+1. Add an anonymous content runtime object in the "contentRuntimes" array.
+1. Set the "id" property of the object to a descriptive name.
+1. Set the "code.page" object to the full URL of the custom content that you want to embed in the document.
+1. Optionally, set the "requestedWidth" and "requestedHeight" properties to a size between 32 and 1000 pixels. If these properties aren't used, the Office application determines the size.
+1. Optionally, set the "disableSnapshot" property to `true` to prevent Office from saving a snapshot of the content component with the document. 
+
+The following is an example of a "contentRuntimes" property.
+
+```json
+"contentRuntimes": [
+    {
+        "id": "ContentRuntime",
+        "code": {
+            "page": "https://localhost:3000/content.html"
+        },
+        "requestedWidth": 100,
+        "requestedHeight": 100,
+        "disableSnapshot": true,
+    }
+]
+```
+
+# [XML Manifest](#tab/xmlmanifest)
 
 - For the **\<[OfficeApp](/javascript/api/manifest/officeapp)\>** element, set the `xsi:type` attribute to `"ContentApp"`.
 - In the **\<[DefaultSettings](/javascript/api/manifest/defaultsettings)\>** element, add the **\<[RequestedHeight](/javascript/api/manifest/requestedheight)\>** and  **\<[RequestedWidth](/javascript/api/manifest/requestedwidth)\>** elements.
 
+---
+
 For a sample that implements a content add-in, see [Excel Content Add-in Humongous Insurance](https://github.com/OfficeDev/Excel-Content-Add-in-Humongous-Insurance) on GitHub.
 
 To create your own content add-in, see the [Excel content add-in quick start](../quickstarts/excel-quickstart-content.md) and [PowerPoint content add-in quick start](../quickstarts/powerpoint-quickstart-content.md).