docs: add build tools to Table of Contents (#3228)

Author: fyzhu

website/architecture/architecture-overview.md

@@ -20,4 +20,6 @@ Architecture Overview is intended to share conceptual overview of how React Nati
   - [Cross Platform Implementation](xplat-implementation)
   - [View Flattening](view-flattening)
   - [Threading Model](threading-model)
+- Build Tools
+  - [Bundled Hermes](bundled-hermes)  
 - [Glossary](glossary)