New action: chain

[madx]

New action: chain

This new action would help combining to actions without having to declare multiple handlers with on. Here's an example to demonstrate its use:

on("click", "button", chain(
  toggle("hide", "p"),
  toggle("hide", "ul"),
))

[madx]

Support for this should instead be baked in to avoid having a new function in the API, I think we could use rest arguments or allow an array as the last parameter instead

[madx]

This is baked in in the on function now