Support company and flex msg

What's Changed

• refactor: remove UID argument from NotionDB methods by @kkdai in #17
• Refactor flex message structure by @kkdai in #18
• Fix properties in AddPageToDatabase function by @kkdai in #19
• refactor: refactor AddPageToDatabase function to use Person struc… by @kkdai in #20

Full Changelog: v0.6.0...v0.7.0