Throw error when multiple versions specified

[karlhorky]

Followup to #33 and #35 by @Jack-Works

Throws error if multiple versions of pnpm are specified, both in:

• in the GitHub Action config with the key "version"
• in the package.json with the key "packageManager"

This will avoid ERR_PNPM_BAD_PM_VERSION errors as documented here:

• https://github.com/pnpm/action-setup/issues/105#issuecomment-2066183978

cc @KSXGitHub

[karlhorky]

@KSXGitHub @zkochan is there anything left to resolve here? Can this be merged?

[zkochan]

I guess this is a breaking change

[karlhorky]

Thanks for the review, the commit improving the robustness of the error condition and merge!

I would also agree that this is a breaking change - I will keep an eye on the releases for v4:

• https://github.com/pnpm/action-setup/releases/tag/v4.0.0