Bump major version in README

[injust]

The READMEs for https://github.com/fish-shop/install-fish-shell and https://github.com/fish-shop/indent-check are both still @v1.

You probably want the suggested usage to be on the latest major version?

[injust]

https://github.com/fish-shop/indent-check as well, btw (I don't think it's worth opening a 2nd issue on that repo).

[marcransome]

👍🏻 Fixed in fish-shop/indent-check#244.