fix: prevent pnpm from removing dev deps while in production

[ntnyq]

Description

This PR adds an args --prod=false to installPackage function for pnpm.

Prevent it from removing installed devDeps while NODE_ENV is production

Linked Issues

Fix #18

Additional context

Refs:

• https://pnpm.io/cli/install#--prod--p

Besides

@iconify/utils and @unocss/preset-icons need to be updated after this is addressed.

I'm encountering this from using unocss.

[antfu]

I don't know. Isn't this too specific to your case? Why NODE_ENV is production in your case?

[ntnyq]

I don't know. Isn't this too specific to your case? Why NODE_ENV is production in your case?

I removed @iconify/json from deps and added autoInstall: true to presetIcons.

Then run build script, let unocss do the rest.

[ntnyq]

I'm wondering is there any case people need to remove already installed devDeps while installing deps.

If so, maybe we could add an option and fix this case in iconify repo.