document how to set options, see #19

docs/options.md

@@ -1,5 +1,20 @@
 # Options
 
+You can customize the plugin by setting options in `mkdocs.yml`. For example:
+
+=== ":octicons-file-code-16: mkdocs.yml"
+
+  ```yaml
+  plugins:
+    - charts:
+        vega_width: container
+        vega_theme: default
+        vega_theme_dark: dark
+        vega_renderer: svg
+        use_data_path: True
+        data_path: ""
+  ```
+
 - `vega_width` (default is `container`). When not specified explicitly in the JSON schema, the `width` to use (see [vegalite customizing size](https://vega.github.io/vega-lite/docs/size.html)). When set to `container` width will be 100%.
 - `vega_theme` (default is `default`). Specify one of the available [vegalite themes](https://vega.github.io/vega-themes/).
 - `vega_theme_dark` (default is `dark`). When using the [mkdocs-material](https://squidfunk.github.io/mkdocs-material) theme with a dark mode, automatically render charts using this theme. Dark mode toggle is also supported. Specify one of the available [vegalite themes](https://vega.github.io/vega-themes/).