docs: make it clear for extnames, see #214

docs/source/tutorials/options.md

@@ -45,8 +45,8 @@ LiquidJS defaults this option to <code>true</code> to be compatible with shopify
 **extname** defines the default extname to be appended into filenames if the filename has no extname. Defaults to `''` which means it's disabled by default. By setting it to `.liquid`:
 
 ```liquid
-{% render "foo" %}  loads foo.liquid
-{% render "foo.html" %}  loads foo.html
+{% render "foo" %}  there's no extname, adds `.liquid` and loads foo.liquid
+{% render "foo.html" %}  there is an extname already, loads foo.html directly
 ```
 
 {% note info Legacy Versions %}

docs/source/tutorials/partials-and-layouts.md

@@ -12,9 +12,9 @@ color: '{{ color }}' shape: '{{ shape }}'
 
 // file: theme.liquid
 {% assign shape = 'circle' %}
-{% render 'color' %}
-{% render 'color' with 'red' %}
-{% render 'color', color: 'yellow', shape: 'square' %}
+{% render 'color.liquid' %}
+{% render 'color.liquid' with 'red' %}
+{% render 'color.liquid', color: 'yellow', shape: 'square' %}
 ```
 
 The output will be:
@@ -27,6 +27,10 @@ color: 'yellow' shape: 'square'
 
 More details please refer to the [render](../tags/render.html) tag.
 
+{% note tip The ".liquid" Extension %}
+The ".liquid" extension in <code>layout</code>, <code>render</code> and <code>include</code> an be omitted if Liquid instance is created using `extname: ".liquid"` option. See <a href="./options.html#extname">the extname option</a> for details.
+{% endnote %}
+
 ## Layout Templates (Extends)
 
 For the following template files:
@@ -38,7 +42,7 @@ Header
 Footer
 
 // file: page.liquid
-{% layout "default-layout" %}
+{% layout "default-layout.liquid" %}
 {% block content %}My page content{% endblock %}
 ```