[E2] Provide information on how to create an API plugin

I appreciate that the lab gives you a starting point so that you don't have to deal with lot of boilerplate JSON but, as someone who is approaching API plugins for the first time, I find it a bit confusing because, once I have completed the lab, I have no idea on how to create a new one on my own.

I think it would be beneficial to:

• Keep the copy & paste approach but, in the intro of the exercise, add a paragraph that explains how you have created the plugin definition

OR

• Let the user create the plugin given the API URL and then replace the generated content with the one provided in the starting project.

The second one would be more effective, but I understand it's more challenging because the API URL isn't fixed and, in the plugin definition, it's defined with a variable.