Improve -S (built-in webserver) to support optional ca/crt/key arguments

Description

This would be nice just because for somebody who just wants to run a simple PHP application in a Docker container and set it up behind Cloudflare; they little more than suggest that you establish end-to-end encryption and even provide you with a certificate bundle to use with your application. In general I prefer less complexity for anything that I actually have to maintain, so if at most all I have to run is 1 container (which serves the PHP application with php -S) then it's a much better deal for me than having to mess around with nginx, or apache.

首先定位 PHP 内置 Web 服务器的实现及其对 -S 选项的处理方式。定义应如何接受可选的 ca、crt 和 key 参数，并验证 PHP 应用程序可以在 Cloudflare 后使用它们实现 HTTPS。