add BooleanWildcard (#14)

README.md

@@ -70,6 +70,7 @@ final class MyUnitTest extends TestCase
 This ignores the concrete uuid given for the field "id" and only checks that a valid uuid is provided.
 
 The library currently supports the following wildcards:
+- BooleanWildcard
 - IntegerWildcard
 - UuidWildcard
 - DateTimeWildcard

src/Wildcard/BooleanWildcard.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace KigaRoo\SnapshotTesting\Wildcard;
+
+use function is_bool;
+
+final class BooleanWildcard implements Wildcard
+{
+    /** @var string */
+    private $path;
+
+    public function __construct(string $path)
+    {
+        $this->path = $path;
+    }
+
+    public function atPath() : string
+    {
+        return $this->path;
+    }
+
+    /**
+     * @param mixed $mixed
+     */
+    public function match($mixed) : bool
+    {
+        return is_bool($mixed);
+    }
+}