6.4.0

Feature

• Add getLinkToken API (#96)
• Handle req.rawBody in Google Cloud Functions (#101)
• [Kitchensink] Add ngrok functionality (#99)

Type

• Add types for video in imagemap message (#100)
• Add contentProvider fields to content messages (#103)
• Add destination field to webhook request body (#102)
• Add MemberJoinEvent and MemberLeaveEvent types (#107)

Misc

• Don't include doc in released source
• Upgrade TypeScript to 3.1.6 (#94)
• Refactoring (#94, #98, #99)
• Remove webhook-tester tool