Include /tests in the /wasm-game-of-life tree

[fbitti]

When going through the steps of the book on Dec 27th, the directory created by cargo generate --git https://github.com/rustwasm/wasm-pack-template includes the folder tests and the web.rs file inside it. Either we should update the tree or include a note that the contents may vary depending on the template's version, because, on a tutorial, it is very important that all steps are really clear so that, when something unrelated fails, the learner is not uncomfortable that something like this might be the cause.

✋ A similar PR may already be submitted! Comment: I searched and didn't find a similar submission.

[jtescher]

Noticed this as well. Is there something stopping this PR from being merged?

[socketbox]

This is still an oversight in the description of the tree. After cargo generate --git https://github.com/rustwasm/wasm-pack-template, tests/web.rs exists.