Add registration button for Virtual IoT & Edge Days 2023

Resolves #712 (closed)

data/en/eclipse-virtual-iot-2023/registration.yml

 title: About the Event 
-end_date: 2023-05-17
+end_date: 2023-05-18
 end_text: |
-  Thanks to everyone who helped make Virtual IoT & Edge Days 2022 such a success, especially our speakers, program committee, and member companies.
+  Thanks to everyone who helped make Virtual IoT & Edge Days 2023 such a success, especially our speakers, program committee, and member companies.
+links:
+  - url: 'https://www.crowdcast.io/e/may16&17_iot&edgedays'
+    text: Register Now