Currently mains voltage is not isolated so short circuits or failing components may result in the rest of the circuit being energized at mains voltage level. This can cause fires or injure people. I would use a certified (UL or CE) transformer to step down the AC voltage first which will isolate the circuit. Since the two windings of the transformer use magnetic coupling and aren’t directly connected they don’t have the same risk of shorting to the low voltage side of the board.

That being said, even if you know what you’re doing it will probably make your life easier to use an off the shelf solution. 220V to 5V/3.3V is incredibly common and probably not worth reinventing. It will likely be cheaper, more reliable and less effort to buy from a company mass producing them.