docs: added agent authentication func

README.md

@@ -82,6 +82,7 @@ Please refer to JSDoc for more details.
 | Method name                        | Description                                                     |
 |------------------------------------|-----------------------------------------------------------------|
 | `fetchAppToken`                    | fetch API token for communication with Crowdin API              |
+| `fetchAgentToken`                  | fetch Agent API token for communication with Crowdin API        |
 | `generateOAuthToken`               | generates OAuth token for communication with Crowdin API        |
 | `refreshOAuthToken`                | refresh OAuth token in case if it was expired                   |
 | `constructCrowdinIdFromJwtPayload` | creates unique id of crowdin user and project from the context  |