fix Windows 11/10 ISO download 404 error (#24)

[sumeshi]

This fixes the win11/10x64 404 download error reported in the issue.

Due to recent changes on Microsoft’s side, the legacy HTML-based API
no longer reliably generates ISO download URLs.
This update switches the Windows consumer download flow to use
the software-download-connector JSON API.

While jq is used in quickemu-project/quickemu as mentioned in the issue,
this project intentionally avoids jq to keep dependencies minimal.

Note that not all downloads are fixed by this change.
Some media still fail as shown below, likely due to different causes.

Windows media	Before	After
win7x64-ultimate	○	○
win81x64	×	×
win10x64	×	○
win11x64	×	○
win81x64-enterprise-eval	○	○
win10x64-enterprise-eval	×	×
win11x64-enterprise-eval	×	×
win10x64-enterprise-ltsc-eval	×	×
win2008r2	○	○
win2012r2-eval	○	○
win2016-eval	○	○
win2019-eval	○	○
win2022-eval	○	○

[sumeshi]

#24

[Seneral]

Sadly, I now get error 400 for both win10x64 and win11x64, without a VPN (with I just get IP blocks).
Tried changing my user-agent in the script to my browsers one, no difference.
Downloading straight from the website using that browser & user-agent worked.