You're fine putting the receptacle there
You have a common-trip, two-pole breaker (instead of two handle-tied single pole breakers or an independent trip breaker), so that meets the disconnecting and OCP requirements for a mixed 120/240V circuit (210.4(C) Exception 2), and since the motor FLA is only 8A, it doesn't exceed the 50% (10A) limit on hardwired loads where receptacles or luminaires are also present (210.23(A)(2)).
Since the breaker is 20A and this will no longer be a motor-only circuit, not only do you need to use 12AWG wire for the connection to the new receptacle, you need to make sure the existing wiring is all 12AWG or thicker, and replace any substandard wire found. Also, make sure the motor has a built-in thermal overload protector or is impedance protected as per 430.32(B) and 430.53(B). (Look for a red button on the motor, or the letters 'T.P.' or 'Z.P.' on the motor nameplate.)