Downloads: Add winget download instrunctions

Adds support for downloading Windows PHP binaries using `winget`.

Both TS and NTS builds are now available on `microsoft/winget-pkgs`[1]
repo, and I have been maintaining them for a while now.

When a new PHP release is found, the manifests are automatically[^2]
built and the manifests are attested[^3]. I submit PRs[^4] after
manually checking if everything is in order.

This PR updates the new `downloads.php` page with `winget`-specific
download instructions.

 - When the Usage field is set to CLI, the winget instructions refer to
   NTS builds (e.g `PHP.PHP.NTS.8.4`)
 - Other Usage values use the TS builds (e.g. `PHP.PHP.8.4`).

[^1]: https://github.com/microsoft/winget-pkgs/tree/master/manifests/p/PHP/PHP
[^2]: https://github.com/PHPWatch/php-winget-manifest/
[^3]: https://github.com/PHPWatch/php-winget-manifest/attestations
[^4]: https://github.com/microsoft/winget-pkgs/pulls?q=is%3Apr+%5BPHP%5D

downloads.php

@@ -88,6 +88,7 @@ $os = [
             'windows-native' => 'Single Line Installer',
             'windows-chocolatey' => 'Chocolatey',
             'windows-scoop' => 'Scoop',
+            'windows-winget' => 'Winget',
             'windows-docker' => 'Docker',
             'windows-wsl-debian' => 'WSL/Debian',
             'windows-wsl-ubuntu' => 'WSL/Ubuntu',