Update install prerelease instructions

[carolynvs]

What does this change

• Update the hard-coded version in the example commands
• Copy over improvements from the main website in our links and wording that was missed when I synced main into v1.

What issue does it fix

N/A

Notes for the reviewer

N/A

Checklist

• Did you write tests?
• Did you write documentation?
• Did you change porter.yaml or a storage document record? Update the corresponding schema file.
• If this is your first pull request, please add your name to the bottom of our Contributors list. Thank you for making Porter better! 🙇‍♀️

Reviewer Checklist

• Comment with /azp run test-porter-release if a magefile or build script was modified
• Comment with /azp run porter-integration if it's a non-trivial PR