downloads: make the download page more readable
The downloads page currently contains a bit of an infodump.
From my own small qualitative surverys, the main feedback I've heard is:
- actual links only take you to the stable page
- it's not at all clear that the device names are hyperlinks.
- The download links are also quite small.
- Many people aren't even aware of the useful information in the notes below the downloads.
I've address this by removing a lot of the unecessary content on the page and rewriting what's there to be easier to parse while skim reading. I separated the download links from the device names and let the table fill the full width. It should still be clear that edge is not generally recommended, but it's now much easier to find for a developer who may be new to postmarketOS.