context.php: add Dependency Injection container implementation

inc/context.php

@@ -0,0 +1,31 @@
+<?php
+namespace Vichan;
+
+defined('TINYBOARD') or exit;
+
+class Context {
+	private array $definitions;
+
+	public function __construct(array $definitions) {
+		$this->definitions = $definitions;
+	}
+
+	public function get(string $name): mixed {
+		if (!isset($this->definitions[$name])) {
+			throw new \RuntimeException("Could not find a dependency named $name");
+		}
+
+		$ret = $this->definitions[$name];
+		if (is_callable($ret) && !is_string($ret) && !is_array($ret)) {
+			$ret = $ret($this);
+			$this->definitions[$name] = $ret;
+		}
+		return $ret;
+	}
+}
+
+function build_context(array $config): Context {
+	return new Context([
+		'config' => $config,
+	]);
+}