enhance: Document and update examples in s3 (#816)

Author: LaurenceJJones

crowdsec-docs/docs/log_processor/data_sources/s3.md

@@ -14,6 +14,7 @@ To monitor a S3 bucket detecting new objects from a SQS queue:
 source: s3
 polling_method: sqs
 sqs_name: test-sqs-s3-acquis
+use_time_machine: true
 labels:
   type: foo
 ```
@@ -24,10 +25,15 @@ source: s3
 polling_method: list
 bucket_name: my_bucket
 polling_interval: 30
+use_time_machine: true
 labels:
   type: foo
 ```
 
+:::warning
+It is **strongly recommended** to set `use_time_machine: true` when using the S3 data source. Since files from S3 are not read in real time, the parser must rely on the timestamps within the log lines themselves to process events accurately.
+:::
+
 :::warning
 The `list` polling method is mostly intended for testing purposes, and its usage is not recommended in production.
 It won't work well with moderately big buckets (tens of thousands of files), as the listing operation is slow.
@@ -127,4 +133,4 @@ You can specify the `log_level` parameter to change the log level for the acquis
 crowdsec -type syslog -dsn s3://my_bucket/my_prefix/foo.log?log_level=debug
 ```
 
-AWS SDK behaviour can be configured with the standard AWS environment variables.
+AWS SDK behaviour can be configured with the standard AWS environment variables.