Add some usage notes

README.md

@@ -18,4 +18,29 @@ This command will download and install the shortcode extension under the `_exten
 
 ## Usage
 
-Add more details
+We presently support the following shortcodes:
+
+| Shortcode  | Description                                                     |
+|------------|-----------------------------------------------------------------|
+| `audio`    | Embeds an audio player with optional caption and download link. |
+| `pdf`      | Embeds a PDF file with customizable width and height.           |
+| `revealjs` | Embeds a Reveal.js slide deck with optional height.             |
+
+You can use the shortcode immediately in a Quarto project that has the extension installed by typing into the document:
+
+```md
+{{< shortcode-name filename >}}
+```
+
+For example, we can embed RevealJS slides using:
+
+```md
+{{< revealjs "assets/my-slides.html" >}}
+```
+
+## Help
+
+To report a bug, please [add an issue](https://github.com/coatless-quarto/embedio/issues/new) to the repository's [bug tracker](https://github.com/coatless-quarto/embedio/issues).
+
+Want to contribute a feature? Please open an issue ticket to discuss the feature before sending a pull request. 
+