Add --vcs option for "new" subcommand

[carlosouro]

💡 Feature description

In Cargo, --vcs enables us to discard default git repository initialisation (--vcs none), or use a separate VCS instead.
It would be good to have the same ability in wasm-pack, in particular --vcs none.

💻 Basic example

The option --vcs none is of particular importance for when we want to use wasm-pack combined with eg. wasm-pack-plugin to create an embedded wasm module within an app existing git repo, without having to publish it through NPM separately.

wasm-pack new appHelper --vcs none