enh: async dynamic generator actions

[benallfree]

This update makes it possible to use a dynamic actions function that returns a promise. It's helpful for situations where building the final actions list requires async calls.

[akaguny]

i'm also need this feature!
in logic that change looks like "simple dimple"
change
actions = actions(data);
to
actions = await actions(data);
in the condition

    // if action is a function, run it to get our array of actions
    if (typeof actions === "function") {
      actions = await actions(data);
    }

if actions function is async then we wait, in another way nothing changed.
yes, it can maybe be a little slowly, but is that really matter and if we have benchmarks we can check

[benallfree]

Yep and it seems to work 100%!

[akaguny]

@benallfree , you know what we should do for the next iteration of the implementation?

[benallfree]

The PR is ready & awaiting approval. What do you mean next iteration?