Add CoyoteCert to PHP libraries

[bashgeek]

This PR adds CoyoteCert to the PHP libraries section.

CoyoteCert is a modern ACME v2 client library for PHP 8.3+. It implements the full RFC 8555 protocol along with RFC 8738 (IP address identifiers) and RFC 9773 (Automatic Renewal Information). The library is framework-agnostic, has no SDK dependencies for its DNS providers, and supports HTTP-01, DNS-01, and TLS-ALPN-01 challenge types.

Built-in providers cover Let's Encrypt, ZeroSSL, Google Trust Services, SSL.com, and Buypass. Six DNS-01 handlers are included out of the box (Cloudflare, Hetzner, DigitalOcean, ClouDNS, Route53, and shell/exec).

• Repository: https://github.com/blendbyte/CoyoteCert
• Packagist: https://packagist.org/packages/blendbyte/coyotecert
• Documentation: see README.md in the repository

Submission checklist

• The client respects the Let's Encrypt trademark policy. CoyoteCert has no Let's Encrypt branding, logos, or implied affiliation.
• The client is not browser-based and supports automatic renewals via issueOrRenew() and a CLI (coyote issue).
• The client encourages routine renewals at randomized times. The README's automatic renewal examples include a sleep $((RANDOM % 3600)) jitter in the cron command, with a note explaining why.
• This commit adds CoyoteCert to the end of the PHP libraries section.
• This commit updates the lastmod date stamp at the top of clients.json.