docs: add Yii 3 page

[KalimeroMK]

Add a documentation page for Yii 3, similar to the existing Laravel and Symfony pages:

• Running a Yii 3 app with the FrankenPHP Docker image
• Installing and running locally with a Caddyfile
• Worker mode via the official yiisoft/yii-runner-frankenphp package, including the watch directive for development, the MAX_REQUESTS environment variable, and a note about resetting stateful services

The examples follow the Yii app template structure (public/ webroot) and the configuration validated in the runner package README.

Closes yiisoft/yii-runner-frankenphp#5

[AlliBalliBaba]

It's a bit more efficient to have the root inside php_server

Suggested change

	localhost {
	# Set the webroot to the public/ directory
	root public/
	# Enable compression (optional)
	encode zstd br gzip
	# Execute PHP files from the public/ directory and serve assets
	php_server {
	try_files {path} index.php
	}
	}
	localhost {
	# Enable compression (optional)
	encode zstd br gzip
	# Execute PHP files from the public/ directory and serve assets
	php_server {
	root public/
	try_files {path} index.php
	}
	}

[AlliBalliBaba]

Not familiar with Yii, but wouldn't you want to send all request to the worker (via match *)

Suggested change

	localhost {
	root public/
	encode zstd br gzip
	php_server {
	worker {
	file ./worker.php
	# Reload workers when PHP files change (development only)
	watch ./**/*.php
	}
	}
	}
	localhost {
	encode zstd br gzip
	php_server {
	root public/
	worker ./worker.php {
	# send all requests to the worker
	match *
	# Reload workers when PHP files change (development only)
	watch ./**/*.php
	}
	}
	}