- Some more documentation made / fixed

docs/01-echoing.md

@@ -30,7 +30,7 @@ Using `print` or `echo`, which are, by default, made safer by using PHP's native
 
 **[PHP]** Would yield internally:
 
-```php
+```html
 <?php echo htmlspecialchars((string) "Hello World !", 3, 'UTF-8', true) ?>
 
 <?php echo htmlspecialchars((string) "This is another way to output &lt;safe&gt; content", 3, 'UTF-8', true) ?>
@@ -63,7 +63,7 @@ Those tokens represents the equivalent of the printf() function from PHP.
 
 **[PHP]** Would render internally as :
 
-```php
+```html
 <?php 
     $num = 5; 
     $location = 'tree';

docs/10-extension-custom.md

@@ -0,0 +1,4 @@
+# Extension - Creating an extension
+
+
+

docs/10-extension-json.md

@@ -0,0 +1,4 @@
+# Extension - `json`, `json.pretty`, `json.html`
+
+This extension 
+