Update build_docs.py for page titles (#6574)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

docs/build_docs.py

@@ -83,6 +83,21 @@ def update_html_links():
     print(f'Total number of links updated: {total_updated_links}')
 
 
+def update_page_title(file_path: Path, new_title: str):
+    """Update the title of an HTML file."""
+
+    # Read the content of the file
+    with open(file_path, encoding='utf-8') as file:
+        content = file.read()
+
+    # Replace the existing title with the new title
+    updated_content = re.sub(r'<title>.*?</title>', f'<title>{new_title}</title>', content)
+
+    # Write the updated content back to the file
+    with open(file_path, 'w', encoding='utf-8') as file:
+        file.write(updated_content)
+
+
 def main():
     # Build the docs
     build_docs()
@@ -93,6 +108,9 @@ def main():
     # Show command to serve built website
     print('Serve site at http://localhost:8000 with "python -m http.server --directory site"')
 
+    # Update titles
+    update_page_title(SITE / '404.html', new_title='Ultralytics Docs - Not Found')
+
 
 if __name__ == '__main__':
     main()