feat: add robots and sitemap generation, enhance documentation page with copy markdown button

- Introduced `robots.ts` for defining robots.txt rules and sitemap URL.
- Added `sitemap.ts` to generate a sitemap based on available documentation pages.
- Enhanced the documentation page to include a "Copy as Markdown" button for easy copying of content.
- Created `copy-markdown-button.tsx` component for clipboard functionality.
- Implemented `llms.txt` route to provide a text-based overview of documentation links.

apps/docs/app/docs/[[...slug]]/page.tsx

@@ -1,4 +1,5 @@
-import { getPageImage, source } from "@/lib/source";
+import { CopyMarkdownButton } from "@/components/copy-markdown-button";
+import { getPageImage, getLLMText, source } from "@/lib/source";
 import { getMDXComponents } from "@/mdx-components";
 import {
 	DocsBody,
@@ -16,10 +17,14 @@ export default async function Page(props: PageProps<"/docs/[[...slug]]">) {
 	if (!page) notFound();
 
 	const MDX = page.data.body;
+	const markdown = await getLLMText(page);
 
 	return (
 		<DocsPage toc={page.data.toc} full={page.data.full}>
-			<DocsTitle>{page.data.title}</DocsTitle>
+			<div className="flex items-center justify-between">
+				<DocsTitle>{page.data.title}</DocsTitle>
+				<CopyMarkdownButton markdown={markdown} />
+			</div>
 			<DocsDescription>{page.data.description}</DocsDescription>
 			<DocsBody>
 				<MDX