Updated Arch Linux external references

[kjkent]

Updates to the Arch Linux subsection within "Unofficial Packages" docs. External link now points to current package page on archlinux.org, and the maintainer email address now reflects the official email found in the Arch PKGBUILD.

Closes #22147

[kjkent]

@sbc100 as requested!

If you feel it would be beneficial, I had a couple of ideas for further edits to this text:

• I noticed that the chocolatey package (for Windows) has not been updated for over a year now. However, Windows has another popular community-run package manager (scoop). They have the current emscripten in their "main" repo, so it should be well-maintained and might make a suitable replacement here. Windows has recently pushed out its official winget package manager, but as it's new it's missing a few things, emscripten being one of them.

• Debian and Ubuntu also package emscripten in their official repos. I would happily add them to the list.

• I could standardise the entries, without or with install commands.

I guess something like:

**Arch Linux**
 - Install with: `pacman -S emscripten`
 - package info: https://archlinux.org/packages/extra/x86_64/emscripten
 - maintainer: Sven-Hendrik Haase <svenstaro@archlinux.org>

**Debian**
 - Install with: `apt install emscripten`
 - Package info: https://packages.debian.org/stable/emscripten
 - Maintainer: The Debian QA Group <packages@qa.debian.org>

**MacOS (requires Homebrew)**
 - Install with: `brew install emscripten`
 - Package info: https://formulae.brew.sh/formula/emscripten
 - Maintainer: `Homebrew <https://github.com/Homebrew/brew>`_

**Ubuntu**
 - Install with: `apt install emscripten`
 - Package info: https://packages.ubuntu.com/noble/emscripten
 - Maintainer: Ubuntu MOTU developers <ubuntu-motu@lists.ubuntu.com>

**Windows (requires Scoop)**
 - Install with `scoop bucket add main & scoop install main/emscripten`
 - Package info: https://github.com/ScoopInstaller/Main/blob/master/bucket/emscripten.json
 - Maintainer: `Scoop <https://github.com/ScoopInstaller/Scoop>`_

[sbc100]

@svenstaro does this look correct to you?

Any other updates to this list are, of course, welcome. However, it would be good to check with those of the upstreams that thier package is ready for the prime time. We have had problems with downstream packaging of emscripten in the past because it contains a bunch of pinned dependencies and this has resulting in several bugs in the past.

[kjkent]

@sbc100 that's a solid point; thanks for letting me know! I'll put it on my todos to ask the packagers. As an aside, emscripten is also packaged as a VCS package (tracks the main branch and builds locally) on the Arch User Repository. The package was orphaned and lacked updates since 2021, so I've adopted it and will bring it up-to-date when I get a minute to look it over :)

Also it has just dawned on me that the individual tagged here and in #22147, and who maintains the Arch package, are all one and the same @svenstaro ! When I saw the thumbs-up reaction, I genuinely stopped, thinking whoah... how'd they find out so fast?...

Apologies for jumping the gun here, I should have waited for @svenstaro to comment! Too eager to contribute :')

[svenstaro]

All good. Feel free to go ahead.