Add community mirror

[inge4pres]

The mirror is geographically redundant and fast thanks to Cloudflare CDN.
Instructions to replicate the same setup are also added in MIRRORS.md.

[linusg]

The "How to use" and "Why choose zigmirror.com?" sections on the marketing website are not in spirit of the Zig community mirror list IMO. Statements like "The fastest community mirror to download Zig binaries" ought to be backed up with numbers.

[inge4pres]

Hey @linusg 👋🏼 thanks for the hint, the website is simply a display page that show the property of the mirror - it's not meant much for marketing but for displaying how it's done, and why.

I actually re-run the numbers since the PR was implemented and noticed that other mirrors have a similar download bandwidth and latency (they can download a cached tarball in ~2 second, and uncached in ~12 secs).
As for availability, it falls back to the Cloudflare SLAs for web and R2, as there are no other components involved, it's a completely managed service.

Let me know if I should update the website, which is not in this repo, for the PR to be accepted.
The failing check in CI does not seem related to the mirror implementation, which I had tested with the check-mirror script.

Here's what I used now just now to check the latency (for cached tarballs)

☁  www.ziglang.org [main] ⚡  curl -iLO https://zigmirror.com/zig-0.14.1.tar.xz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
100 16.9M  100 16.9M    0     0  6589k      0  0:00:02  0:00:02 --:--:-- 9080k
☁  www.ziglang.org [main] ⚡  curl -iLO https://pkg.machengine.org/zig/zig-0.14.1.tar.xz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 16.9M  100 16.9M    0     0  2309k      0  0:00:07  0:00:07 --:--:-- 2071k
☁  www.ziglang.org [main] ⚡  curl -iLO https://zigmirror.hryx.net/zig/zig-0.14.1.tar.xz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 16.9M  100 16.9M    0     0  2284k      0  0:00:07  0:00:07 --:--:-- 3604k
☁  www.ziglang.org [main] ⚡  curl -iLO https://zig.florent.dev/zig-0.14.1.tar.xz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 16.9M  100 16.9M    0     0  4004k      0  0:00:04  0:00:04 --:--:-- 4004k
☁  www.ziglang.org [main] ⚡  curl -iLO https://zig.mirror.mschae23.de/zig/zig-0.14.1.tar.xz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 16.9M  100 16.9M    0     0  8931k      0  0:00:01  0:00:01 --:--:-- 8931k
☁  www.ziglang.org [main] ⚡  curl -iLO https://zigmirror.meox.dev/zig-0.14.1.tar.xz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 16.9M    0 16.9M    0     0  7551k      0 --:--:--  0:00:02 --:--:-- 7552k

[mlugg]

Sorry it's taken me so long to look at this.

Yes, I'd like to ask for the front page to be modified. Like @linusg, I'm not a fan of how the content of that page pits this community mirror against others; the whole point of the community mirror project is to cooperate to improve everyone's experience by distributing the task of serving tarballs and eliminating SPOFs. Regardless of the numbers, I would like to request that:

• The line "The fastest community mirror to download Zig binaries" be removed. (The mention of "fastest" is the problem; a less boastful subtitle is of course fine.)
• The "How to use" section be either removed, or replaced with instructions for using the general community mirrors system (i.e. probably just a link to Community Mirrors). The whole point of this system is that people shouldn't hardcode to a single mirror.
• The "Why choose zigmirror.com" section be either removed, or renamed to something less competitive-seeming (e.g. "Features", "Performance", "About this mirror", or similar).

Personally, I would prefer if the landing page were entirely replaced, either with a simple page containing details about this mirror, or even just with a redirect to Community Mirrors. However, I'd be okay with merging given the changes listed above; I just don't want any mirror to paint itself as superior to others and thereby encourage fragmentation within the ecosystem of mirrors. Thank you!