fix: check packages existence in local scope

[paescuj]

Description

• Use explicit scope path for existence checks of ESLint/Prettier plugin deps
• Skip installation of missing packages if current working directory is not in scope of @antfu/eslint-config

Linked Issues

Fixes #581

Additional context

• The existence check for packages that aren't directly used, but just control the config (e.g. typescript) is not changed, as for those it makes sense to look in current working directory.

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