Finch user-specific data directory

[ningziwen]

Finch macOS is currently storing user-specific data in ~/.finch. I learned from the conversation in Notation about the best practice for user-specific data in macOS is another directory. notaryproject/notation#473 (comment)

I don't have more details for now but want to raise it here for us to start discussion for the related topics for Finch here, including but not limited to:

• Will Finch have the use case for MacOS sandbox?
• Should Finch change to macOS preferred directory by 1.0? If yes, migration plan?
• Does other platform such as Windows have the similar concern?
• We are working on supporting Windows. Support Finch on Windows #492 Taking this concern into consideration, what is the best directory to choose in Windows?