Support description and syntax in reference by .property.yml

[gaocegege]

Now we have example code and image, but no description and syntax

[jeremydouglass]

Excellent.

Are the image assets being taken from the original Processing(Java) reference site, or are we generating the images from our reference sketches?

[gaocegege]

We will generate the image by

# Original example code
saveFrame(''docs/img/arc1.png')
exit()

Just like your idea for e2e test. 😄

[jeremydouglass]

Very fun. Reference materials and e2e test -- I'm excited!