If you already have a battery and charging circuit working with a uUSB connector, then it can be as easy as plugging in an aftermarket XI receiver. They cost about $8, when you get them from China. The bases you can get anywhere nowadays, even Ikea has them.
If you don’t, well then get that first! That’s the tricky part I think, seeing how finicky the pie is with its power supply.
Be aware that wireless charging does generate some heat, plus its really slow. You might not want that.
I would opt for a solution where both wired and wireless charging would be possible.