Update README.md, consistent use of spaces instead of tabs, better examples

bin/counting_stopped_workers.php

@@ -0,0 +1,24 @@
+<?php
+
+use Toalett\Multiprocessing\ContextBuilder;
+use Toalett\Multiprocessing\Task\Interval;
+
+require_once __DIR__ . '/../vendor/autoload.php';
+require_once __DIR__ . '/classes/Counter.php';
+const NUM_JOBS = 50;
+
+$context = ContextBuilder::create()
+    ->withCleanupInterval(Interval::seconds(0.5))
+    ->build();
+
+$counter = new Counter();
+$context->on('worker_stopped', [$counter, 'increment']);
+$context->on('no_workers_remaining', [$context, 'stop']);
+$context->on('stopped', fn() => printf(" %d\n", $counter->value));
+
+for ($i = 0; $i < NUM_JOBS; $i++) {
+    $context->submit(fn() => sleep(2));
+    print('.');
+}
+
+$context->run();