MDL-69548 core: Adding the ZipStream library

This allows downloading of zip files as a stream, and will be used by
the Download course content project (MDL-69540).

lib/zipstream/src/Exception/StreamNotReadableException.php

@@ -0,0 +1,22 @@
+<?php
+declare(strict_types=1);
+
+namespace ZipStream\Exception;
+
+use ZipStream\Exception;
+
+/**
+ * This Exception gets invoked if `fread` fails on a stream.
+ */
+class StreamNotReadableException extends Exception
+{
+    /**
+     * Constructor of the Exception
+     *
+     * @param string $fileName - The name of the file which the stream belongs to.
+     */
+    public function __construct(string $fileName)
+    {
+        parent::__construct("The stream for $fileName could not be read.");
+    }
+}