markdown export from URL (#5830)

* Add Markdown export of any doc page by appending `.md` to the URL
* New "View as Markdown" dropdown menu from the "copy page" button

documentation/plugins/markdown-export.cjs

@@ -0,0 +1,61 @@
+const fs = require('fs');
+const path = require('path');
+const globby = require('globby');
+
+module.exports = function markdownExportPlugin(context, options) {
+  const pluginOptions = {
+    enabled: true,
+    ...options,
+  };
+
+  return {
+    name: 'markdown-export',
+    
+    async postBuild({ outDir }) {
+      if (!pluginOptions.enabled) {
+        return;
+      }
+
+      console.log('[markdown-export] Starting markdown export...');
+      
+      const docsDir = path.join(context.siteDir, 'docs');
+      const outputDir = path.join(outDir, 'docs');
+      
+      // Get all markdown files
+      const files = await globby('**/*.{md,mdx}', { cwd: docsDir });
+      
+      for (const file of files) {
+        const inputPath = path.join(docsDir, file);
+        const outputPath = path.join(outputDir, file.replace('.mdx', '.md'));
+        
+        // Ensure output subdirectory exists
+        fs.mkdirSync(path.dirname(outputPath), { recursive: true });
+        
+        const content = fs.readFileSync(inputPath, 'utf-8');
+        
+        // Strip frontmatter and clean up
+        const cleaned = stripFrontmatter(content);
+        
+        // Write the cleaned markdown alongside HTML files
+        fs.writeFileSync(outputPath, cleaned);
+      }
+      
+      console.log(`[markdown-export] Successfully exported ${files.length} markdown files to ${outputDir}`);
+    },
+  };
+};
+
+function stripFrontmatter(content) {
+  // Remove YAML frontmatter (everything between --- at the start)
+  const withoutFrontmatter = content.replace(/^---\s*\n[\s\S]*?\n---\s*\n/, '');
+  
+  // Clean up any remaining import statements (for .mdx files)
+  const withoutImports = withoutFrontmatter.replace(/^import .+$/gm, '');
+  
+  // Remove excessive empty lines and trim
+  return withoutImports
+    .replace(/\n{3,}/g, '\n\n')
+    .trim();
+}
+
+