Filter md's title hide in summary.md

example:
```md
# Summary

### Getting Started

* [About this documentation](README.md)
* [Installation and Setup](setup.md)

### Your Content

* [Directory structure](structure.md)
* [Pages and Summary](pages.md)
* [Configuration](config.md)
* [Glossary](lexicon.md)
* [Multi-Lingual](languages.md)
* [Markdown](syntax/markdown.md)
* [Headings](syntax/markdown.md#headings)
* [Paragraphs](syntax/markdown.md#paragraphs)
* [Emphasis](syntax/markdown.md#emphasis)
* [Lists](syntax/markdown.md#lists)
* [Links](syntax/markdown.md#links)
* [Images](syntax/markdown.md#images)
* [Blockquotes](syntax/markdown.md#blockquotes)
* [Tables](syntax/markdown.md#tables)
* [Code](syntax/markdown.md#code)
* [HTML](syntax/markdown.md#html)
* [Footnotes](syntax/markdown.md#footnotes)
* [AsciiDoc](syntax/asciidoc.md)
* [eBook and PDF](ebook.md)

### Customization

* [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)
* [Blocks](plugins/blocks.md)
* [Filters](plugins/filters.md)
* [API & Context](plugins/api.md)
* [Test your plugin](plugins/testing.md)
* [Theming](themes/README.md)

--

* [FAQ](faq.md)
* [Examples](examples.md)
* [Release notes](https://github.com/GitbookIO/gitbook/blob/master/CHANGES.md)
```