Document `pkgx --sync`

[svenjacobs]

pkgx --sync is currently a hidden gem that helps when the pantry doesn't update automatically for some reason.
Unfortunately that command is not documented anywhere.

[mxcl]

for some reason

I'll fix the bug. While I understand that it is frustrating that this isn't documented, I in general believe that documenting small details can make a tool harder to learn rather than fixing frustrations. It's a balancing act.

I'll add it to an FAQ.

[mxcl]

I notice it is in the verbose help: pkgx --verbose --help. I agree this is hidden, but well, it is somewhere. Still adding to the FAQ.