This PR removes installation instructions for Nx < 18 since it has
fallen out of support window. Users can always `npm install <plugin>` as
usual if they are on an unsupported Nx version, but the docs will assume
`nx add` moving forward.
The changes are on the plugin overview page:
https://nx-dev-git-docs-remove-nx-pre-18-install-nrwl.vercel.app/nx-api
## Current Behavior
Currently it is already possible to use `eslint.config.cjs` because of
this
[line](c655b6cf4f/packages/eslint/src/utils/flat-config.ts (L7)):
However docs section doesn't mention it
## Expected Behavior
This commit is supposed to mention this feature in the plugin
documentation
---------
Co-authored-by: Leosvel Pérez Espinosa <leosvel.perez.espinosa@gmail.com>
