v3.0.0-beta.6

Note that if you had an earlier version of the Kap beta installed, you first need to delete ~/Library/Application Support/Kap Beta/config.json due to changes in the config format.

A few highlights in this release:

• Dark mode support (#644)
• Remember the last used directory (#687)
• Use original file name for exports when possible (#688)
• Added electron-store JSON schema for the app settings (#667)
• Improved error handling
• A number of fixes, improvements, and dependency updates

v3.0.0-beta.5...v3.0.0-beta.6