Add a page for `<Handle>`

[bcakmakoglu]

With this issue I'd like to suggest adding a new page for the <Handle> component and how to use it.

The page could include the following:

1. What is a Handle and why/how to use it
2. What positions are possible (and how to relate them to a container)
3. How to use multiple handles of the same type
4. How to hide handles (not using display: none or visiblity: hidden)
5. How to limit connections to a handle
6. Connection Modes
7. Dynamic Handles and/or dynamic positioning of handles