feature: add a web visualization of the Spoon model

today, we have two visualizations of a Spoon model with Swing and JavaFX.

the limitation is that it requires potential users to have Java and Spoon installed.

to overcome this, we could have a web-based UI: you paste Java code in a text area and you navigate in the spoon model in the browser.

requirements:

* the "wow" effect
* same features than the JavaFX app