Robert on hackaday.io designed this upgrade for a cheap TP4056 Li-Ion charger board:
I wanted to have a load sharing for my future battery operated project with the ability to charge the battery. There is a load of cheap TP4056 boards from China. None of them has the load sharing or voltage regulator on board so I made my own addon board.
Smrtokvitek has shared the board on OSH Park: