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.

まず、PHP 組み込み Web サーバーの実装と、-S オプションの処理方法を特定します。オプションの ca、crt、key 引数をどのように受け付けるべきかを定義し、PHP アプリケーションが Cloudflare の背後で HTTPS にそれらを使用できることを確認します。