feat: multi-language support — PHP, Ruby, Perl, Go (binary-env)

- PHP: ghcr.io/fission/php-env, entrypoint main.php::handler
- Ruby: ghcr.io/fission/ruby-env, entrypoint handler (single-word)
- Perl: ghcr.io/fission/perl-env (version=1), sub {} return value
- Go: ghcr.io/fission/binary-env with pre-compiled binary (shell script placeholder)

Provider changes:
- package_resource: added main.php, main.rb, main.pl to source_dir candidates
- function_resource: relaxed entrypoint validation to allow PHP (::), Ruby, Perl (single-word)
- function_resource_test: updated BadFormat test to reflect new valid formats

examples/php-hello/code/main.php

@@ -0,0 +1,7 @@
+<?php
+function handler($context)
+{
+    /** @var \Psr\Http\Message\ResponseInterface $response */
+    $response = $context["response"];
+    $response->getBody()->write("Hello from PHP in Fission");
+}

examples/php-hello/main.tf

@@ -0,0 +1,39 @@
+terraform {
+  required_providers {
+    fission = {
+      source  = "nail/fission"
+      version = "~> 0.1.0"
+    }
+  }
+}
+
+provider "fission" {
+  kubeconfig_path = "/home/naeel/.kube/config"
+  namespace       = "default"
+}
+
+resource "fission_environment" "php" {
+  name    = "tf-php-hello-env"
+  image   = "ghcr.io/fission/php-env"
+  version = 3
+}
+
+resource "fission_package" "pkg" {
+  name        = "tf-php-hello-pkg"
+  environment = fission_environment.php.name
+  source_dir  = "${path.module}/code"
+}
+
+resource "fission_function" "fn" {
+  name         = "tf-php-hello-fn"
+  environment  = fission_environment.php.name
+  package_name = fission_package.pkg.name
+  entrypoint   = "main.php::handler"
+}
+
+resource "fission_http_trigger" "route" {
+  name     = "tf-php-hello-route"
+  function = fission_function.fn.name
+  url      = "/php-hello"
+  methods  = ["GET"]
+}