refactor: migrate to TypeScript

[mtth]

avsc now builds on three separate packages, which can be imported separately:

• @avro/types, serialization logic
• @avro/streams, object containers
• @avro/idl, AVDL parsing

Breaking changes:

• [ ] type.hash() is now computeHash()
• [ ] type.random() is now randomValue()
• Removed deprecated functions
  • type.getAliases, type.getFingerprint, type.getName, type.getSchema, type.getTypeName.