MM-52642 CLD-6352 MM-54007 Prepare setup for Playwright pipeline (#24647)

* pipeline(playwright): prepare setup for playwright

* feedback address

* clean up readme

* Fix docker-compose command and definition for dashboard

* fix the dashboard

* ignore dashboard when formatting

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Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: Mario Vitale <mvitale1989@hotmail.com>

webapp/channels/src/components/app_bar/app_bar_plugin_component.tsx

@@ -71,6 +71,7 @@ const AppBarPluginComponent = (props: PluginComponentProps) => {
         >
             <img
                 src={iconUrl}
+                alt={component.pluginId}
                 onLoad={onImageLoadComplete}
                 onError={onImageLoadError}
             />