Documentation: refer to latest version (3.0.1)

Documentation:

Install and run quickstart

This document (and others, too) still refer to Antora v3.0.0.

Since we now have Antora v3.0.1, this should be adopted to point to the latest version.

Markup to be adapted:

[subs=+attributes]
 $ node -e "fs.writeFileSync('package.json', '{}')"
 $ npm i -D -E @antora/cli@{page-component-version}.0 @antora/site-generator@{page-component-version}.0