ctx.wizard.step could unwrap before return

[MKRhere]

Currently wizard steps have no idea whether the next/previous middleware are MiddlewareFn or MiddlewareObj, leading to cases like:

ctx.wizard.back();

// This expression is not callable.
// Not all constituents of type 'Middleware<unknown>' are callable.
return ctx.wizard.step(ctx, next);

The fix is:

return Composer.unwrap(ctx.wizard.step)(ctx, next);

v5 could make this change:

get step() {
-  return this.steps[this.cursor]
+  return Composer.unwrap(this.steps[this.cursor])
}

Therefore making it always safe to call ctx.wizard.step?.(ctx. next)