docs(v2): improve static assets docs (#1822)

* docs(v2): improve static assets docs

* docs(v2): improve static assets docs

website/docs/static-assets.md

@@ -5,38 +5,57 @@ title: Static Assets
 
 In general, every website needs assets: images, stylesheets, favicons and etc. In such cases, you can create a directory named `static` at the root of your project. Every file you put into that directory will be copied into the the root of the generated `build` folder with the directory hierarchy preserved. E.g. if you add a file named `sun.jpg` to the static folder, it’ll be copied to `build/sun.jpg`.
 
-This means that if the site's `baseUrl` is `/`, an image in `/static/img/docusaurus_keytar.svg` is available at `<baseUrl>/docusaurus_keytar.svg`.
+This means that if the site's `baseUrl` is `/`, an image in `/static/img/docusaurus_keytar.svg` is available at `/img/docusaurus_keytar.svg`.
 
 <!-- TODO: Yangshun: This is inaccurate for sites with a non '/' baseUrl -->
 
 ## Referencing your static asset
 
-You can reference assets from the static folder in your code with absolute path, i.e. starting with a slash /.
+You can reference assets from the `static` folder in your code. You could use hardcoded absolute paths, i.e. starting with a slash /, but remember to include the `baseUrl` if it is not `/`. However, this will break if you change your `baseUrl` in the config.
 
-### Markdown example
-
-```markdown
-<!-- reference static/img/docusaurus.png -->
-
-![Docusaurus logo](/img/docusaurus.png)
-```
-
-Result:
-
-![Docusaurus logo](/img/docusaurus.png)
+A better way would be to use the `withBaseUrl` utility function which appends the `baseUrl` to paths for you.
 
 ### JSX example
 
 ```jsx
-// reference static/img/slash-birth.png
-<img src="/img/slash-birth.png" alt="docusaurus mascot" />
+// MyComponent.js
+import withBaseUrl from '@docusaurus/withBaseUrl';
+
+<img
+  alt="Docusaurus with Keytar"
+  src={withBaseUrl('img/docusaurus_keytar.svg')}
+/>;
 ```
 
-Result:
+### Markdown example
 
-<img src="/img/slash-birth.png" alt="docusaurus mascot" />
+Thanks to MDX, you can also use `withBaseUrl` utility function in Markdown files! You'd have to use `<img>` tags instead of the Markdown image syntax though. The syntax is exactly the same as in JSX.
+
+```txt
+// my-doc.mdx
+---
+id: my-doc
+title: My Doc
+---
+
+import withBaseUrl from '@docusaurus/withBaseUrl'; // Add to the top of the file below the front matter.
+
+...
+
+<img alt="Docusaurus with Keytar" src={withBaseUrl('img/docusaurus_keytar.svg')} />;
+```
+
+You could also just use Markdown image syntax, but you would have to manually maintain the image paths yourself and isn't recommended.
+
+```md
+// my-doc.md
+
+![Docusaurus with Keytar](/img/docusaurus_keytar.png)
+```
+
+### Caveats
 
 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 result in a 404 error.
+- By default, none of the files in `static` folder will be post-processed or minified.
+- Missing files references via hardcoded absolute paths will not be detected at compilation time, and will result in a 404 error.