Reorganize downloads

[LilithHafner]

• Move latest stable release number higher on the page (on my default full-screen resolution this brings it from below the fold to above the fold)
• Stop recommending jill.py
• Move juliaup to the top of platform specific instructions instead of the bottom
• Place support tiers above manual instillation
• Minor reorderings
  • Put combined Linux & Mac juliaup instructions above Windows instead of below (they were below because, historically, JuliaUp was a windows-only tool.
  • Bring Linux to the top of the platform specific manual instillation instructions because Linux users are imo the most likely to choose manual instillation over the recommended juliaup
  • Place SHA256 before MD5 because it's cryptographically secure

[github-actions]

Once the build has completed, you can preview your PR at this URL: https://julialang.netlify.app/previews/PR2001/ in ~15 minutes

[IanButterworth]

LGTM but can we merge this first? #2005

[IanButterworth]

Let's address @KristofferC's comments here #2005 (comment)

[KristofferC]

I noticed now I actually made a mistake when reading the note about Juliaup... I thought it said "The recommended installation method is via the Juliaup"... but it actually says "This recommended installation method is via the Juliaup...". So it isn't as "bad" as I originally thought but could maybe be slightly reworded anyway...

[IanButterworth]

Yeah I was trying to get in "recommended" but I think that's implicit so doesn't need to be there.

[IanButterworth]

As for the width, do you think it should go full width? Originally I had it narrower. It's supposed to stand out like a call-out. If it's full width the box padding will still mean the text is inset from the text below and on a mobile browser the edge of the box is up against the edge of the screen.

[KristofferC]

Maybe it is fine the way it is 🤷. Could possibly work better by having some delimiter between the box and the rest of the text or maybe just some extra vertical whitespace to make it feel a bit less connected to the text under it. But feel free to ignore.

[IanButterworth]

All good suggestions. Thanks. Updated.

and on a mobile browser the edge of the box is up against the edge of the screen.

This actually isn't true. The edge is inset.

[IanButterworth]

This looks good to me now. @LilithHafner I'll let you final review and merge given I made changes