Add 11.0 folder with global.json for .NET 11 previews

Adds the 11.0 sample folder with a global.json pinned to the .NET 11
preview SDK. Uses rollForward: latestFeature and allowPrerelease: true
so it will automatically pick up newer preview builds.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jfversluis

11.0/global.json

@@ -0,0 +1,7 @@
+{
+  "sdk": {
+    "version": "11.0.100-preview.2.26159.112",
+    "rollForward": "latestFeature",
+    "allowPrerelease": true
+  }
+}