feat(app) add documentation site template (#879)

* Added site

* update

* Added overview section

* Added skeleton

documentation/blog/2021-08-26-welcome/index.md

@@ -0,0 +1,25 @@
+---
+slug: welcome
+title: Welcome
+authors: [slorber, yangshun]
+tags: [facebook, hello, docusaurus]
+---
+
+[Docusaurus blogging features](https://docusaurus.io/docs/blog) are powered by the [blog plugin](https://docusaurus.io/docs/api/plugins/@docusaurus/plugin-content-blog).
+
+Simply add Markdown files (or folders) to the `blog` directory.
+
+Regular blog authors can be added to `authors.yml`.
+
+The blog post date can be extracted from filenames, such as:
+
+- `2019-05-30-welcome.md`
+- `2019-05-30-welcome/index.md`
+
+A blog post folder can be convenient to co-locate blog post images:
+
+![Docusaurus Plushie](./docusaurus-plushie-banner.jpeg)
+
+The blog supports tags as well!
+
+**And if you don't want a blog**: just delete this directory, and use `blog: false` in your Docusaurus config.