fix: add the snippets directory by default

[jdrouet]

This should fix #1206

I don't know what is the way to detect if the snippets directory should be included so, by default, I include it considering it's already in the sideEffect section.
Another possibility would be to add to the Cargo.toml metadata a package-json section that allows to add some files and enforce it there.

Tell me if it's ok with you or if you need some updates 😉

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