update README

README.md

 # mth-grid (BETA VERSION)
 
+[![pipeline status](https://forgemia.inra.fr/metabohub/web-components/mth-grid/badges/master/pipeline.svg)](https://forgemia.inra.fr/metabohub/web-components/mth-grid/-/commits/master)
+[![npm package](https://img.shields.io/gitlab/v/tag/metabohub%2Fweb-components%2Fmth-grid?gitlab_url=https%3A%2F%2Fforgemia.inra.fr%2F)](https://forgemia.inra.fr/metabohub/web-components/mth-grid/-/packages)
+
+
+The storybook documentation is available [here](https://metabohub.pages.mia.inra.fr/web-components/mth-grid/).
+
 ## Types
 
 | Name | Value |
@@ -26,6 +32,7 @@
 | Name        | Description                                                                               | Type of `$event`    |
 | ----------- | ----------------------------------------------------------------------------------------- | ------------------- |
 | `selection` | triggered when the list of currently selected rows changes | `MthGridItem[]` |
+| `selectedHeaders` | the headers currently displayed in the table | `MthGridHeader[]` |
 
 ## Slots