Share a reactive value with createPulse

Create a reactive value, update it, and notify the mounted view that reads it.

The example increments the current value and renders `Count: 1`; a separate path can rerun subscribers without changing that value.

import { mount } from "valyrian.js";
import { createPulse } from "valyrian.js/pulses";

const [count, setCount] = createPulse(0);

setCount((current) => current + 1);

mount("body", () => `Count: ${count()}`);