Update README.md

Author: lfoppiano

README.md

@@ -43,8 +43,9 @@ In the following table the list of parameters that can be provided to the `pdf_v
 | annotations             | A list of annotations to be overlaid on the PDF. Format is described here.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
 | pages_vertical_spacing  | The vertical space (in pixels) between each page of the PDF. Defaults to 2 pixels.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
 | annotation_outline_size | Size of the outline around each annotation in pixels. Defaults to 1 pixel.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
-| rendering               | Type of rendering: `unwrap` (default), `legacy_iframe`, or `legacy_embed`. The default value, `unwrap` shows the PDF document using pdf.js, and supports the visualisation of annotations. Other values are `legacy_iframe` and `legacy_embed` which use the legacy approach of injecting the document into an `<embed>` or `<iframe>`. These methods enable the default pdf viewer of Firefox/Chrome/Edge that contains additional features we are still working to implement in this component. **NOTE**: Annotations are ignored for both 'legacy_iframe' and 'legacy_embed'. |
-| pages_to_render         | Filter the rendering to a specific set of pages. By default all pages are rendered.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
+| rendering               | Type of rendering: `unwrap` (default), `legacy_iframe`, or `legacy_embed`. The default value, `unwrap` shows the PDF document using pdf.js, and supports the visualisation of annotations. Other values are `legacy_iframe` and `legacy_embed` which use the legacy approach of injecting the document into an `<embed>` or `<iframe>`. They allow viewing the PDF using the viewer of the browser that contains additional features we are still working to implement in this component. **IMPORTANT**: :warning: The "legacy" methods **work only with Firefox**, and **do not support annotations**. :warning:|
+| pages_to_render         | Filter the rendering to a specific set of pages. By default, all pages are rendered.        |                                                                                                                                                                                                                                                                                                                                          
+
 
 ### Annotation format 
 The annotations format has been derived from the [Grobid's coordinate formats](https://grobid.readthedocs.io/en/latest/Coordinates-in-PDF/), which are described as a list of "bounding boxes".