ENH: Add copilot-setup-steps.yml with pixi installation

Co-authored-by: thewtex <25432+thewtex@users.noreply.github.com>

Author: Copilot

.github/copilot-setup-steps.yml

@@ -0,0 +1,5 @@
+name: Setup ITK Development Environment
+timeout-minutes: 0
+steps:
+  - name: Set up Pixi
+    uses: prefix-dev/setup-pixi@v0.8.1