Include example forms in the documentation

[ghost]

Is your feature request related to a problem? Please describe.
Some people might not know how to use Contact Form 7 or how to create a simple sign-up form.

Describe the solution you'd like
Add a simple, example sign-up form into the documentation. It should have a name field, email field and submit button.

Describe alternatives you've considered
Demonstrate all of the plugin capabilities via different example forms included in the documentation.