Add doc for inline rendering

docs/SUMMARY.md

@@ -31,6 +31,7 @@
 * [Templating](templating/README.md)
     * [Content References](templating/conrefs.md)
     * [Variables](templating/variables.md)
+    * [Builtin](templating/builtin.md)
 * [Plugins](plugins/README.md)
     * [Create a plugin](plugins/create.md)
     * [Hooks](plugins/hooks.md)

docs/plugins/api.md

@@ -12,6 +12,14 @@ var value = book.config.get('title', 'Default Value');
 
 // Resolve a filename to an absolute path
 var filepath = book.resolve('README.md');
+
+// Render an inline markup string
+book.renderInline('markdown', 'This is **Markdown**')
+    .then(function(str) { ... })
+
+// Render a markup string (block mode)
+book.renderBlock('markdown', '* This is **Markdown**')
+    .then(function(str) { ... })
 ```
 
 #### Output instance

docs/templating/builtin.md

@@ -0,0 +1,18 @@
+# Builtin Templating Helpers
+
+GitBook provides a serie of builtin filters and blocks to help you write templates.
+
+### Filters
+
+`value|default(default, [boolean])`If value is strictly undefined, return default, otherwise value. If boolean is true, any JavaScript falsy value will return default (false, "", etc)
+
+`arr|sort(reverse, caseSens, attr)`
+Sort arr with JavaScript's arr.sort function. If reverse is true, result will be reversed. Sort is case-insensitive by default, but setting caseSens to true makes it case-sensitive. If attr is passed, will compare attr from each item.
+
+### Blocks
+
+`{% markdown %}Markdown string{% endmarkdown %}`
+Render inline markdown
+
+`{% asciidoc %}AsciiDoc string{% endasciidoc %}`
+Render inline asciidoc