Add support for phpclass reference with namespace

Author: alamirault

src/Reference/PhpClassReference.php

@@ -29,10 +29,11 @@ public function getName(): string
 
     public function resolve(Environment $environment, string $data): ResolvedReference
     {
+        $classnamePath = str_replace('\\', '-', strtolower($data));
         return new ResolvedReference(
             $environment->getCurrentFileName(),
             $data,
-            sprintf('%s/class.%s.php', $this->phpDocUrl, strtolower($data)),
+            sprintf('%s/class.%s.php', $this->phpDocUrl, $classnamePath),
             [],
             [
                 'title' => $data,

tests/fixtures/expected/blocks/references/php-class.html

@@ -1 +1,2 @@
 <p><a href="https://secure.php.net/manual/en/class.arrayaccess.php" class="reference external" title="ArrayAccess" rel="external noopener noreferrer" target="_blank">ArrayAccess</a></p>
+<p><a href="https://secure.php.net/manual/en/class.bcmath-number.php" class="reference external" title="BcMath\Number" rel="external noopener noreferrer" target="_blank">BcMath\Number</a></p>

tests/fixtures/source/blocks/references/php-class.rst

@@ -1,2 +1,4 @@
 
 :phpclass:`ArrayAccess`
+
+:phpclass:`BcMath\Number`