Add DatePickerExample to Linux CI

Author: bbrk24

.github/workflows/build-test-and-docs.yml

@@ -298,7 +298,8 @@ jobs:
         swift build --target StressTestExample && \
         swift build --target SpreadsheetExample && \
         swift build --target NotesExample && \
-        swift build --target GtkExample
+        swift build --target GtkExample && \
+        swift build --target DatePickerExample
 
     - name: Test
       run: swift test --test-product swift-cross-uiPackageTests