2.2.1

• Added missing version property to Statement
• Corrected to Timestamp type for stored and timestamp properties on Statement
• Added missing SubStatement interface (See https://github.com/adlnet/xAPI-Spec/blob/master/xAPI-Data.md#substatements)
• Corrected StatementObject union type to use SubStatement instead of Statement
• Updated dependencies
• Updated CI to test against node v16.x