Add copilot swe agent setup instructions (#377)

Author: AArnott

.github/workflows/copilot-setup-steps.yml

@@ -0,0 +1,41 @@
+name: "Copilot Setup Steps"
+
+# Automatically run the setup steps when they are changed to allow for easy validation, and
+# allow manual testing through the repository's "Actions" tab
+on:
+  workflow_dispatch:
+  push:
+    branches:
+    - main
+    paths:
+    - .github/workflows/copilot-setup-steps.yml
+  pull_request:
+    paths:
+    - .github/workflows/copilot-setup-steps.yml
+
+jobs:
+  # The job MUST be called `copilot-setup-steps` or it will not be picked up by Copilot.
+  copilot-setup-steps:
+    runs-on: ubuntu-latest
+    # Set the permissions to the lowest permissions possible needed for your steps.
+    # Copilot will be given its own token for its operations.
+    permissions:
+      # If you want to clone the repository as part of your setup steps, for example to install dependencies, you'll need the `contents: read` permission. If you don't clone the repository in your setup steps, Copilot will do this for you automatically after the steps complete.
+      contents: read
+
+    # You can define any steps you want, and they will run before the agent starts.
+    # If you do not check out your code, Copilot will do this for you.
+    steps:
+    - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+      with:
+        fetch-depth: 0 # avoid shallow clone so nbgv can do its work.
+    - name: ⚙ Install prerequisites
+      run: |
+        ./init.ps1 -UpgradePrerequisites -NoNuGetCredProvider
+        dotnet --info
+
+        # Print mono version if it is present.
+        if (Get-Command mono -ErrorAction SilentlyContinue) {
+          mono --version
+        }
+      shell: pwsh