See PostCSS docs for examples for your environment.
Also you can get all build-in easings:
Allow to set custom easings:
easings: easeJump: 'cubic-bezier(.86,0,.69,1.57)'
Plugin will convert custom easing name between camelCase and snake-case.
So example below adds
Custom easing name must start from
ease and contain only letters and
You can create custom easing on cubic-bezier.com.