docs(v2): add docs on static assets (#1648)

* docs(v2
): add docs on static assets

* Update static-assets.md

website/docs/static-assets.md

@@ -3,15 +3,40 @@ id: static-assets
 title: Static Assets
 ---
 
-_This section is a work in progress. [Welcoming PRs](https://github.com/facebook/docusaurus/issues/1640)._
+In general, every website needs assets: images, stylesheets, favicons and etc. In such cases,
+you can create a folder named `static` at the root of your project. Every file you put into that folder will be copied into the generated build folder. E.g. if you add a file named `sun.jpg` to the static folder, it’ll be copied to `build/sun.jpg`
 
-A "how-to" guide on including static assets within pages and docs.
+This means that if the site's baseUrl is `/`, an image in `static/img/docusaurus_keytar.svg` is available at `docusaurus_keytar.svg`.
 
-<!--
-### Images
-### Videos
 
-**References**
-- https://v1.vuepress.vuejs.org/guide/assets.html
-- https://www.gatsbyjs.org/docs/images-and-files/
--->
+## Referencing your static asset
+
+You can reference assets from the static folder in your code with absolute path, i.e. starting with a slash /.
+
+Markdown example:
+
+```markdown
+<!-- reference static/img/docusaurus.png -->
+![docusaurus logo](/img/docusaurus.png)
+```
+
+Result:
+
+![docusaurus logo](/img/docusaurus.png)
+
+JSX example:
+
+```jsx
+// reference static/img/slash-birth.png
+<img src="/img/slash-birth.png" alt="docusaurus mascot" />
+```
+
+Result:
+
+<img src="/img/slash-birth.png" alt="docusaurus mascot" />
+
+
+Keep in mind that:
+
+- None of the files in static folder will be post-processed or minified.
+- Missing files will not be called at compilation time, and will cause 404 errors for your users.