Very pretty game - I was gonna talk about coyote time but looks like comments have already discussed it. Another similar jump related mechanic I would look into would be Autojump. Essentially, with standard jump controls you would need to press jump as soon as you land in order to jump again in succession. However, if you're early, nothing happens, which can make control feel difficult at times. How i would go about implementing autojump is by starting a timer if the player presses jump and is not on the ground, and if the player touches the ground before the timer goes off, jump again. Its one of those things that you dont really think about, but makes games feel much more polished.
Aesthetically very pretty game. Well done!