Documentation: detail how to pass a preset to `run()`

[benjie]

import type {} from "graphile-config";
import { run } from "graphile-worker";
import { WorkerProPreset } from "@graphile-pro/worker";

const preset: GraphileConfig.Preset = {
  extends: [WorkerProPreset],
  worker: {
    /* Your worker config options here */
    connectionString: process.env.DATABASE_URL,
    maxPoolSize: 10,
    // ...
  },
};

const promise = run({ preset });

This needs detailing both on the library page and the worker pro page.