Integrate content from Sean cookbook

[juliendelplanque]

I sent a mail to Sean to see how we can collaborate as he started a wiki on his side.
He answered positively so I added him as contributor of Pharo wiki.

He has an interesting page named "cookbook" from which we could profit: https://github.com/seandenigris/pharo/wiki/Cookbook.

This issue is made for discussing what we could integrate from there.