MM-53962: Adding ES8 dependency (#24399)

* Adding ES8 dependency

```release-note
NONE
```


Co-authored-by: Mattermost Build <build@mattermost.com>

webapp/platform/types/src/config.ts

@@ -795,6 +795,7 @@ export type AnalyticsSettings = {
 
 export type ElasticsearchSettings = {
     ConnectionURL: string;
+    Backend: string;
     Username: string;
     Password: string;
     EnableIndexing: boolean;