[Feature] Performe actions in timeline

[Ladvace]

Is your feature request related to a problem? Please describe.
I don't know if there is already a way to do that but I would like to run some js code (whatever) between steps in a timeline

Describe the solution you'd like

const sequence = [
  ["nav", { x: 100 }, { duration: 1 }],
  // run some code here
  [{ action: ()  => {
  // code
  }],
  ["nav li", { opacity: 1 }, { duration: 0.3, delay: stagger(0.1) }],
]

timeline(sequence)

[marpe]

related to #130