docs(install): Write full supported versions

[Princesseuh]

Hello!

I'm not too picky on the exact format, so feel free to reformat in a way you prefer, but I found it confusing how the "semver" version mention in the docs wasn't accurate, >= 18.17.0 implies that any versions after 18.17.0 works, but that is not the case. For instance, someone on 20.2.x will fail to install Sharp, as will someone on 19.x.x.

This caused a few downstream issues in repos I maintain that have Sharp as an optionalDependencies because users didn't get an error on install (since it's an optionalDep), but as far as they could tell from the Sharp docs, they had a supported version of Node.

[lovell]

Brilliant, thank you very much for this Erika.

[lovell]

I also added a runtime check via commit 45e8071

[Princesseuh]

Awesome, thank you! I unfortunately had to pin the Sharp version used on my projects to 0.32.6 for now, since I still support Node >=18.14.1 (and generally support more Yarn, npm etc versions), but will be updating to Sharp 0.33.0 for sure once we make our semver checks more strict.

Thank you very much for your work on Sharp, you deserve way more help from the ecosystem.