Easing property

There's a list of default easing functions instead of using cubic-bezier directly:

Easing Functions
"linear"	"ease"	"ease-in"	"ease-out"	"ease-in-out"
"ease-in-cubic"	"ease-out-cubic"	"ease-in-out-cubic"
"ease-in-circ"	"ease-out-circ"	"ease-in-out-circ"
"ease-in-expo"	"ease-out-expo"	"ease-in-out-expo"
"ease-in-quad"	"ease-out-quad"	"ease-in-out-quad"
"ease-in-quart"	"ease-out-quart"	"ease-in-out-quart"
"ease-in-quint"	"ease-out-quint"	"ease-in-out-quint"
"ease-in-sine"	"ease-out-sine"	"ease-in-out-sine"
"ease-in-back"	"ease-out-back"	"ease-in-out-back"

We can set it to a custom function like cubic-bezier(0.25, 0.1, 0.25, 1), that's equal to ease.