Zero package manager installer for "scala" command

[bishabosha]

Can we support an installer script for "scala" that does not rely on any other tool (e.g. like the VirtusLab bash script installer at https://scala-cli.virtuslab.org/get)

The command basically detects OS/CPU and installs the corresponding zip from scala3 releases as "scala" - useful for guides on other websites/resources where scala is required but without wanting to decide on a specific package manager (or personal preference where package managers in general are not desired).

previous discussion: scala/docs.scala-lang#3169 which wanted to put a single installer on the "Getting Started" page way to install at https://docs.scala-lang.org/getting-started/install-scala.html

choice:

• install globally, like current, where it goes into the PATH
• should it be a "bootstrap" script (like with gradlew and mill) that stays in the place it is downloaded (and points to a well-known cached location) - personally i dont think its best for now - this would mean rewriting docs to be ./scala, also requires comitting two scripts for windows compat

Aim is to avoid the confusion of so many tools and it seems there is sentiment still that coursier is "yet another" tool.

[tgodzik]

Should we just copy what we have in https://scala-cli.virtuslab.org/get ? We can put it somewhere on scala-lang