Add new format parameter to parse_link hook data

- Add new handling of hook result with JSON format

mod/parse_url.php

@@ -126,14 +126,18 @@ function parse_url_content(App $a)
 
 	$template = '[bookmark=%s]%s[/bookmark]%s';
 
-	$arr = ['url' => $url, 'text' => ''];
+	$arr = ['url' => $url, 'format' => $format, 'text' => null];
 
 	Hook::callAll('parse_link', $arr);
 
-	if (strlen($arr['text'])) {
+	if ($arr['text']) {
+		if ($format == 'json') {
+			System::jsonExit($arr['text']);
+		} else {
 			echo $arr['text'];
 			exit();
 		}
+	}
 
 	// If there is already some content information submitted we don't
 	// need to parse the url for content.