Update wp-now documentation (#251)

Updating the wp-now README file.

packages/wp-now/PUBLISHING.md

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+# Publishing
+
+The `wp-now` package is part of a larger [monorepo](https://github.com/WordPress/playground-tools), sharing its space with other sibling packages.
+
+To publish the `wp-now` package to [npm](https://www.npmjs.com/package/@wp-now/wp-now), you must first understand the automated release process facilitated by lerna.
+
+> [!TIP]
+> For more information on Lerna and other tools used in Playground, check out the [Architecture overview](https://wordpress.github.io/wordpress-playground/architecture/index) chapter over on Playground's comprehensive documentation site.
+
+This process includes automatically incrementing the version number, creating a new tag, and publishing all modified packages to npm simultaneously. Notably, all published packages **share the same version number**.
+
+ Each package identifies a distinct organization in its `package.json` file.
+
+ To publish the `wp-now` package, you need access to the `@wp-now` npm organization.
+
+ To initiate the publishing process for `wp-now`, execute the following commands:
+
+ ```bash
+ npm login # this is required only once and it will store the credentials in ~/.npmrc file.
+ npm run build
+ npm run release:wp-now
+ ```