update docs

Author: khvn26

README.md

@@ -66,9 +66,17 @@ Flagsmith uses Prometheus to track performance metrics.
 
 The following default metrics are exposed:
 
+##### Common metrics
+
 - `flagsmith_build_info`: Has the labels `version` and `ci_commit_sha`.
 - `http_server_request_duration_seconds`: Histogram labeled with `route`, `path`, and `response_status`.
 - `http_server_requests_total`: Counter labeled with `route`, `path`, and `response_status`.
+- `task_processor_enqueued_tasks_total`: Counter labeled with `task_identifier`.
+
+##### Task Processor metrics
+
+- `task_processor_finished_tasks_total`: Counter labeled with `task_identifier` and `result` (`"success"`, `"failure"`).
+- `task_processor_task_duration_seconds`: Histogram labeled with `task_identifier` and `result` (`"success"`, `"failure"`).
 
 ##### Guidelines