adding ch3 as a seperate file

todo.md

@@ -0,0 +1,25 @@
+# xDapp Architecture
+
+- [xDapp Design]()
+  - [Key Considerations]()
+  - [Ecosystems]()
+    - [EVM]()
+    - [Solana]()
+    - [Cosmos]()
+    - [Algorand]()
+  - [Protocol-First Design]()
+  - [Topology]()
+    - [Hub & Spoke]()
+    - [Mesh]()
+  - [xAssets]()
+  - [Relayers]()
+    - [Generic Relayers]()
+    - [Protocol-Specific Relayers]()
+  - [Security]()
+    - [Trust Assumptions]()
+    - [Layer 1 Risk]()
+    - [Finality Guarantees]()
+  - [Examples]()
+    - [Cross-Chain Dex]()
+    - [Remote Staking]()
+  - [Common Use Cases]()