Add the default values to the first example

[rlafuente]

We use default values (e.g. size (100,100), nostroke, yellow fill color) different than in vanilla shoebot.

It makes sense to show these on the first example that's rendered on a page.

Or if that's too complicated, just add them to the first example of the commands page in the docs.

[rlafuente]

added them to the docs example (commit), let's call it a day