Is it safe to connect VCC to a data pin on Attiny chips?
As mentioned by @chrisl, here you would need a pull-down resistor to make sure that pin was not high when the button was not pushed.
It is more typical to connect the button between the IO pin and ground since then you can use the built-in pull-up resistors to make sure the pin is high when the button is not pushed. (This chip only has built-in pull-ups, although some chips have pull-downs).