Have the doc command automatically reload things upon change in the browser

[alexarchambault]

When running things like

$ scala-cli doc . -w

it would be nice to:

• maybe open the doc index.html in the browser (there's a Java API for that IIRC)
• have it auto-reload upon changes (so that changes in the sources would automatically load in the browser), like how docusaurus does in watch mode (like when running cd website && yarn && yarn run start from the Scala CLI sources)