Configure CI workflow to compile AceTime library example

This change causes the "Compile Examples" CI workflow to compile AceTime library's "HelloDateTime" example sketch for
every board in the job matrix.

Author: per1234

.github/workflows/compile-examples.yml

@@ -53,6 +53,7 @@ jobs:
         - ~/Arduino/libraries/MFRC522/examples/rfid_read_personal_data
         - ~/Arduino/libraries/MFRC522/examples/rfid_write_personal_data
         - ~/Arduino/libraries/WiFi101/examples
+        - ~/Arduino/libraries/AceTime/examples/HelloDateTime
 
     strategy:
       fail-fast: false