Add maxLength property to the docs page

Hi Team,

Can we please add the maxLength property to the canonical fields docs page?
This will help customers understand the failure reasons and max length allowed for canonical properties.

https://docs.snowplow.io/docs/understanding-your-pipeline/canonical-event/
https://github.com/snowplow/iglu-central/blob/master/schemas/com.snowplowanalytics.snowplow/atomic/jsonschema/1-0-0