Add link to 1.0 release branch (#211)

Author: angelazhangmsft

README.md

@@ -62,6 +62,7 @@ The easiest way to use these samples without Git is to download the ZIP file. Se
 
 The samples will be updated with GA releases of the Windows App SDK. The `main` branch includes the latest samples, which may also include experimental or preview features. Specific release branches are named `release/x.y` and contain samples that reference the corresponding GA version of the Windows App SDK. This repository currently includes the following release branches:
 
+- [release/1.0](https://github.com/microsoft/WindowsAppSDK-Samples/tree/release/1.0)
 - [release/0.8](https://github.com/microsoft/WindowsAppSDK-Samples/tree/release/0.8)
 - [release/0.5](https://github.com/microsoft/WindowsAppSDK-Samples/tree/release/0.5)