docs/VictoriaLogs: document how to export logs from VictoriaLogs

While at it, mention vmctl-like tool for migrating logs from other systems to VictoriaLogs at docs/VictoriaLogs/Roadmap.md

Thanks to the question from Xavier Pestel at https://www.linkedin.com/feed/update/urn:li:activity:7212093021301927937?commentUrn=urn%3Ali%3Acomment%3A%28activity%3A7212093021301927937%2C7212171550651731969%29&dashCommentUrn=urn%3Ali%3Afsd_comment%3A%287212171550651731969%2Curn%3Ali%3Aactivity%3A7212093021301927937%29

docs/VictoriaLogs/FAQ.md

@@ -127,3 +127,10 @@ On top of this, VictoriaLogs employs additional optimizations for achieving high
   by skipping blocks for unneeded streams when [stream filter](https://docs.victoriametrics.com/victorialogs/logsql/#stream-filter) is used.
 - It maintains sparse index for [log timestamps](https://docs.victoriametrics.com/victorialogs/keyconcepts/#time-field),
   which allow improving query performance when [time filter](https://docs.victoriametrics.com/victorialogs/logsql/#time-filter) is used.
+
+## How to export logs from VictoriaLogs?
+
+Just send the query with the needed [filters](https://docs.victoriametrics.com/victorialogs/logsql/#filters)
+to [`/select/logsql/query`](https://docs.victoriametrics.com/victorialogs/querying/#querying-logs) - VictoriaLogs will return
+the requested logs as a [stream of JSON lines](https://jsonlines.org/). It is recommended specifying [time filter](https://docs.victoriametrics.com/victorialogs/logsql/#time-filter)
+for limiting the amounts of exported logs.

docs/VictoriaLogs/Roadmap.md

@@ -41,3 +41,4 @@ The following functionality is planned in the future versions of VictoriaLogs:
 - Cluster version of VictoriaLogs.
 - Ability to store data to object storage (such as S3, GCS, Minio).
 - Alerting on LogsQL queries.
+- Data migration tool from Grafana Loki to VictoriaLogs (similar to [vmctl](https://docs.victoriametrics.com/vmctl/)).