Overhaul IDE and Installation page

[lihaoyi]

• Added screenshots to the getting started steps for IntelliJ and VSCode

• Put IDE support first, on the assumption that most people will be using an example project with a bootstrap script already set up

• Put global installation last, since it's both very verbose and also unlikely to be used (since we encourage bootstrap scripts)

• Removed a bunch of the command line bloop/bsp instructions, since this is now done transparently by the IDE and wont be of interest to users

• Removed some of the blurb about millw. Having two bootstrap scripts cannot avoid being confusing, we should merge them so there is only one choice going forward.

[lefou]

• Added screenshots to the getting started steps for IntelliJ and VSCode

Nice

• Put IDE support first, on the assumption that most people will be using an example project with a bootstrap script already set up

This assumption don't really match my personal taste or how I digest/consume products.

• Removed some of the blurb about millw. Having two bootstrap scripts cannot avoid being confusing, we should merge them so there is only one choice going forward.

One property of millw is, it provides support for all Mill versions and all operating systems. It also has some convenience features like finding/using the latest released Mill version automatically. In previous discussions we had about this topic, you were against keeping support for older versions in the in-repo script and wanted a rather lean script. That at least is my personal takeaway.

So, having millw follow its own versioning makes sense. It's definitely not the most user friendly setup.

Ideally, we only have one script, and keep the latest version of it as a copy in root of the Mill repo. That follows the scheme we propose as best practice in our documentation.