copying Opta certificates to another location

Opta certificates cannot be shown on Docs when placed in the regular folder, testing if they will be visible from the _unlisted folder.

Author: kateryna-lukina

content/hardware/_unlisted/kits/opta/certifications/Arduino_AFX00001-CERT_UL.pdf

@@ -0,0 +1,9 @@
+---
+title: Opta
+url_shop: https://store.arduino.cc/collections/pro-family
+url_guide: /tutorials/opta/getting-started
+core: arduino:mbed_opta
+certifications: [CE, UL]
+---
+
+The **Arduino Opta®** is a secure, easy-to-use **micro PLC** with Industrial IoT capabilities. Designed in partnership with **Finder®**, a leading industrial and building automation device manufacturer.