Clarify default data directory for `mega`

[MrBeanCpp]

I'm working on the integration of mega and moxin. see PR #147 I need to determine the appropriate directory for storing mega data, which includes:

• log
• database (SQLite)
• cache
• ...

By default, mega data directory is /tmp/.mega.

I noticed these two directories:

• ~/.local/share/moxin
• ~/.config/moxin

Should I use these directories, or is there a more appropriate location for mega data? Any guidance would be appreciated.