add ubuntu 26.04 workflow

.github/workflows/ubuntu2604.yml

@@ -0,0 +1,20 @@
+name: Trigger Ubuntu26.04 CI
+run-name: Ubuntu26.04 - ${{ github.event.pull_request.title }}
+
+on:
+  pull_request_target:
+    types: labeled
+    paths:
+    - 'images/ubuntu/**'
+
+defaults:
+  run:
+    shell: pwsh
+
+jobs:
+  Ubuntu_2604:
+    if: github.event.label.name == 'CI ubuntu-all' || github.event.label.name == 'CI ubuntu-2604'
+    uses: ./.github/workflows/trigger-ubuntu-win-build.yml
+    with:
+      image_type: 'ubuntu2604'
+    secrets: inherit

README.md

@@ -32,7 +32,7 @@ To build a VM machine from this repo's source, see the [instructions](docs/creat
 | Windows Server 2025 with Visual Studio 2026<br>![Endpoint Badge](https://img.shields.io/endpoint?url=https%3A%2F%2Fgist.githubusercontent.com%2Fhosted-runners-images-bot%2F79267492faab096d04cdd25ce7014cec%2Fraw%2Fwin25-vs2026.json) | x64 | `windows-2025-vs2026` | [windows-2025-vs2026] |
 | Windows Server 2025<br>![Endpoint Badge](https://img.shields.io/endpoint?url=https%3A%2F%2Fgist.githubusercontent.com%2Fhosted-runners-images-bot%2F79267492faab096d04cdd25ce7014cec%2Fraw%2Fwin25.json) | x64 | `windows-latest` or `windows-2025` | [windows-2025] |
 | Windows Server 2022<br>![Endpoint Badge](https://img.shields.io/endpoint?url=https%3A%2F%2Fgist.githubusercontent.com%2Fhosted-runners-images-bot%2F79267492faab096d04cdd25ce7014cec%2Fraw%2Fwin22.json) | x64 | `windows-2022` | [windows-2022] |
-| Windows 11 Arm64<br>![Endpoint Badge](https://img.shields.io/endpoint?url=https%3A%2F%2Fgist.githubusercontent.com%2Fhosted-runners-images-bot%2F79267492faab096d04cdd25ce7014cec%2Fraw%2Fwin11-arm64.json) | arm64 | `windows-11-arm64` | [windows-11-arm64] |
+| Windows 11 Arm64<br>![Endpoint Badge](https://img.shields.io/endpoint?url=https%3A%2F%2Fgist.githubusercontent.com%2Fhosted-runners-images-bot%2F79267492faab096d04cdd25ce7014cec%2Fraw%2Fwin11-arm64.json) | arm64 | `windows-11-arm64` | [windows-11-arm64]
 
 ### Label scheme