Resolve "Veto Leak region in postEE 2022 events?"

Closes #48 (closed)

From Junquan's slides. The EE leak issue is well modeled by MC. Since it's optional, I add variables with the suffix _vetoEELeak for vetoing the electrons/photons.

Meanwhile, documented the year condition in json configuration.

I also added some minor updates on the theoretical weights to make the codes compatible with other systematics.