docs(workers): fix start command for local development

[acosoft]

Summary

Fixed local development start command for Docusaurus in Workers docs.

When creating a new project with
pnpm create cloudflare@latest my-docusaurus-app --framework=docusaurus
the generated package.json does not include a dev script. To start the local development server, use pnpm run start.

Here is an example of the default scripts section in the file when the project is created:

	"scripts": {
		"docusaurus": "docusaurus",
		"start": "docusaurus start",
		"build": "docusaurus build",
		"swizzle": "docusaurus swizzle",
		"deploy": "pnpm run build && wrangler deploy",
		"clear": "docusaurus clear",
		"serve": "docusaurus serve",
		"write-translations": "docusaurus write-translations",
		"write-heading-ids": "docusaurus write-heading-ids",
		"typecheck": "tsc",
		"preview": "pnpm run build && wrangler dev"
	}

Screenshots (optional)

The change is highlighted with a green box in the screenshot. pnpm run dev is replaced with pnpm run start.

Documentation checklist

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• The change adheres to the documentation style guide.
• If a larger change - such as adding a new page- an issue has been opened in relation to any incorrect or out of date information that this PR fixes.
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