Implement Unit Tests, add Readme, add examples, stronger implementation

src/ContextBuilder.php

@@ -0,0 +1,39 @@
+<?php
+
+namespace Toalett\Multiprocessing;
+
+use React\EventLoop\Factory;
+use React\EventLoop\LoopInterface;
+
+class ContextBuilder
+{
+    private ?LoopInterface $loop = null;
+    private ?ConcurrencyLimit $limit = null;
+
+    public static function create(): self
+    {
+        return new self();
+    }
+
+    public function withEventLoop(LoopInterface $loop): self
+    {
+        $instance = clone $this;
+        $instance->loop = $loop;
+        return $instance;
+    }
+
+    public function withLimit(ConcurrencyLimit $limit): self
+    {
+        $instance = clone $this;
+        $instance->limit = $limit;
+        return $instance;
+    }
+
+    public function build(): Context
+    {
+        return new Context(
+            $this->loop ?? Factory::create(),
+            $this->limit ?? ConcurrencyLimit::unlimited()
+        );
+    }
+}