More type safety and idiomatic haxe in README

[fullofcaffeine]

Some examples in the README are showing this:

@:liveview
class CounterLive {
    var count = 0;
    
    function mount(_params, _session, socket) {
        return {:ok, assign(socket, "count", count)};
    }
    
    function handle_event("increment", _params, socket) {
        count++;
        return {:noreply, assign(socket, "count", count)};
    }
}

1. This is using plain strings ("count"). We shouldn't be using plain strings or at least they should be typed somehow.
2. the method arguments are using the _ prefix, which is a common idiom in Elixir, but not sure if we can abstract that away in Haxe? Investigate.

Another case of using plain strings that I should double check:

@:changeset  
class UserChangeset {
    @:validate_required(["name", "email"])
    @:validate_format("email", ~r/\S+@\S+\.\S+/)
    static function changeset(user, attrs) {
        // Compiled to proper Ecto.Changeset pipeline
    }
}

See if there's a better idiomatic Haxe typing strategy that I could use here.

[fullofcaffeine]

The phoenix integration examples are rely a lot on strings: https://github.com/fullofcaffeine/reflaxe.elixir/blob/main/documentation/PHOENIX_INTEGRATION_GUIDE.md. Should double check if that provides any type-safety.