leanprover-community installation instructions

Stream: general

[Floris van Doorn]

I propose that we link from https://leanprover-community.github.io/get_started.html prominently to Lean's official installation instructions here: https://docs.lean-lang.org/lean4/doc/quickstart.html
Those installation instructions look excellent to me.

I created a PR for this: leanprover-community.github.io#535 (EDIT: I guess that doesn't work. Here is the link: https://github.com/leanprover-community/leanprover-community.github.io/pull/535 )

[Floris van Doorn]

that was quick :grinning:

[Floris van Doorn]

On the topic of installation instructions, I also opened PR lean4#5559 and issue leanprover/vscode-lean4#529 for minor simplifications in one step of the instructions.