Minor doc fix

docs/source/introduction.rst

@@ -4,6 +4,7 @@ Introduction
 Protein Runway is designed to visualize the essential dynamics for trajectories of large molucules, such as proteins. It focuses on identifying key structural movements using normal mode analysis.
 
 Key Features:
+
 - Visualize molecular trajectories.
 - Extract key movement patterns.
 - Integrate with tools like `Chainsaw`, `Merizo`, `bio3D`.