The MacOS `find` command seems to be case insensitive. So the current
`mailsync` script results in counting each local inbox folder thrice,
resulting in the wrong # of new mails the user is notified about.
The commit implements another `test` command for `$(uname)` to decide
which arguments should be passed to `find`.

_In ref. to :_
https://github.com/LukeSmithxyz/mutt-wizard/issues/157#issuecomment-494132981

Resolves https://github.com/LukeSmithxyz/mutt-wizard/issues/197.

If -a is passed along with "$@", mailsync will sync all mailboxes even
if only a single channel is passed in with "$@". This breaks the
semantics of the `o` macro in mutt which should only sync the current
mailbox that is currently being viewed in mutt.

fix adding new account in macos

Fix mailsync ping command

Fix mutt-wizard

Fix muttrc for mac

Add files for offlineimap_profile and offlineimap_header

Update README with MacOS install instructions