added support for `prism` style code highlighting

by using `class="language-<LANG>"`

src/Parser.php

@@ -344,8 +344,10 @@ class Parser {
 		$lang = count($lang) > 0 ? trim($lang[0]->data) : null;
 
 		$container = $this->document->createElement("pre");
-		if ($lang)
+		if ($lang) {
 			$container->setAttribute("data-lang", $lang);
+			$container->setAttribute("class", "language-$lang");
+		}
 		
 		$buffer = "";
 		while (!($this->current()->type === TokenType::BACKTICK &&
@@ -360,6 +362,10 @@ class Parser {
 		}
 
 		$elm = $this->document->createElement("code", htmlspecialchars($buffer));
+		if ($lang) {
+			$elm->setAttribute("data-lang", $lang);
+			$elm->setAttribute("class", "language-$lang");
+		}
 		$container->appendChild($elm);
 		$this->document->appendChild($container);
 		$this->consume();