Incomplete example in GDNative script page

**Your Godot version:**
v3.4.beta4.mono.official [6a058cbf3]
**Issue description:**
Missing signal connection + missing _ready function
**URL to the documentation page:**
https://docs.godotengine.org/en/stable/tutorials/plugins/gdnative/gdnative-cpp-example.html

ps.: I tried to edit the page and fix it by myself but I receive 404 error. I tried also to pull a request but I'm not familiar yet how to do it in the rigth way

If you know how to fix the issue you are reporting please
consider opening a pull request. We provide a tutorial on
using git here: https://docs.godotengine.org/en/stable/community/contributing/pr_workflow.html,
writing documentation at https://docs.godotengine.org/en/stable/community/contributing/docs_writing_guidelines.html
and contributing to the class reference here: https://docs.godotengine.org/en/stable/community/contributing/updating_the_class_reference.html