Support independent installation

[kopach]

Clear and concise description of the problem

Currently, this tool can be installed only by using one of not package managers from npm registry. While it's convenient for 1 time use, it's a bit frustrating and neglects a bit the main idea every time you update Node.js or just switch node with tools like NVM due to requirements of using exact node version per project. In such a case, @antfu/ni must be installed and updated separatelly per node version

Suggested solution

Please, provide an alternative, system-wide way of installing @antfu/ni. I would really like if there would be possibility to install this tool via brew.
Both pnpm and yarn have available options to be installed via brew just because of this (initially install had to be done npm i -g (same as for @antfu/ni now)

Alternative

Script to install system wide can also be provided (like pnpm does this). Though this solution is OK for non-mac ecosystem, for Mac users brew is way better (except standard easy way to install/uninstall/update it also provide a way to do easy transfer to new system with brewfile and much more)

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guide.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.