copy CNAME

copy CNAME to 'public' to ensure repo 'Settings' --> 'Pages' --> 'Custom domain' is not reset on each deploy (thus causing 404 error at learn.astropy.org).

Author: jeffjennings

.github/workflows/deploy.yaml

@@ -32,10 +32,16 @@ jobs:
 
       - run: npm ci
         name: Install
-
+      
+      - run: cp ./CNAME ./public/CNAME
+        name: Copy CNAME
+        
       - run: npm run build
         name: Build
 
+      - run: echo ./build/CNAME
+        name: check CNAME
+    
       - name: Upload gatsby artifact
         uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02  # v4.6.2
         with: