Replacing Washer outlet with dual receptacle

Current outlet in the laundry room is a single 20 amp dedicated outlet for the washing machine. From what I can determine that was code when my house was built.

Current washer draws 10 amps, I want to add a dryer booster fan that draws .6 amps but have no place to plug it in. So I have two questions.

Is there any issue with replacing the single receptacle with a double as far as code or safety?

I have a new GFCI on hand but it's 15 amps, again is using it an issue as far as code or safety using it on a 20 amp circuit ? Should I just bite the bullet and get a 20 amp GFCI ?

OK, that was three questions ............

Is there a laundry tub within 6' of this rec?
A 15 A duplex is ok on a 20A cir. which gfci's are.

No laundry tub in the laundry room, laundry tub is in the garage which is much more convenient.

Ran into an electrician friend and he recommended staying with a 20 amp outlet. Even though I'm using fewer amps the next owner may put more on the circuit and burn the house down.

Turns out I had a 20 amp GFCI on hand so that's what I used.

A 15a is allowed since each plug is rated for 15a & the device is rated 20a pass thru
Very rare that anything pulls more then 15a from one plug