Common: update CONTRIBUTING.md (closes #3530)
Common: update CONTRIBUTING.md (closes #3530)

RetentionGrid/snowplow,liveintent-berlin/snowplow,liveintent-berlin/snowplow,liveintent-berlin/snowplow,RetentionGrid/snowplow,snowplow/snowplow,liveintent-berlin/snowplow,RetentionGrid/snowplow,RetentionGrid/snowplow,liveintent-berlin/snowplow,snowplow/snowplow,snowplow/snowplow,liveintent-berlin/snowplow,snowplow/snowplow,RetentionGrid/snowplow