Escape text that should not be interpreted as Wiki syntax

_test/json/unformatted.json

@@ -0,0 +1,14 @@
+{
+    "type": "doc",
+    "content": [
+        {
+            "type": "paragraph",
+            "content": [
+                {
+                    "type": "text",
+                    "text": "__foo//bar%%"
+                }
+            ]
+        }
+    ]
+}

_test/json/unformatted.txt

@@ -0,0 +1 @@
+%%__%%foo%%//%%bar<nowiki>%%</nowiki>

parser/TextNode.php

@@ -105,7 +105,25 @@ public function getPostfixSyntax()
 
     public function getInnerSyntax()
     {
-        return $this->text;
+        if ($this->marks['unformatted']) {
+            return $this->text;
+        }
+        return preg_replace_callback(
+            "/\bhttps?:\/\/|__+|\/\/+|%%+|''+|\*\*+/",
+            function ($matches)
+            {
+                switch ($matches[0][0]) {
+                    case 'h':
+                        // We matched http(s)://
+                        return $matches[0];
+                    case '%':
+                        return '<nowiki>' . $matches[0] . '</nowiki>';
+                    default:
+                        return '%%' . $matches[0] . '%%';
+                }
+            },
+            $this->text
+        );
     }