[SUGGESTION] documentation: describe DENO_INSTALL and how to install specific version

[oscar6echo]

Env var DENO_INSTALL is used by install script but nowhere in documentation (I think).
Search for deno env vars, on naturally falls on deno runtime env vars, which naturally does not have DENO_INSTALL.
This is a little puzzling.

How to install a specific version is not immediately available in the doc.
This is currently all the more useful than deno upgrade is buggy behind a proxy.

Suggestions:

• Add env var DENO_INSTALL definition in deno install page
• Add one-liner to install specific version:

  # https://github.com/denoland/deno/releases 
  curl -fsSL https://deno.land/install.sh | sh -s v1.45.2