added some message sending docs

src/SUMMARY.md

@@ -1,7 +1,7 @@
 # Summary
 
 - [Introduction](./introduction/introduction.md)
-    - [What is an xDapp]()
+    - [What is an xDapp](./introduction/xdapp.md)
     - [What is Wormhole]()
     - [What is Portal]()
 - [Wormhole Architecture]()
@@ -25,25 +25,33 @@
         - [MacOS](./development/tilt/mac.md)
         - [Linux](./development/tilt/linux.md)
         - [Constants](./development/tilt/constants.md)
-    - [Project Scaffold]()
+    - [Project Scaffold](./development/scaffold/overview.md)
         - [EVM]()
             - [Foundry]()
         - [Solana]()
             - [Solana CLI]()
             - [Anchor]()
         - [Algorand]()
-    - [Sending Messages]()
-        - [EVM]()
+    - [Sending Messages](./development/messages/sending/overview.md)
+        - [EVM](./development/messages/sending/evm.md)
         - [Solana]()
         - [Algorand]()
-    - [Registering xDapps]()
-        - [EVM]()
+    - [Registering xDapps](./development/messages/registration/overview.md)
+        - [EVM](./development/messages/registration/evm.md)
         - [Solana]()
         - [Algorand]()
+    - [Relaying Messages](./development/messages/relaying/overview.md)
+        - [Rest Relayers]()
+        - [Generic Relayers]()
+        - [Spy Relayer]()
     - [Receving Messages]()
         - [EVM]()
         - [Solana]()
         - [Algorand]()
+- [Portal xDapps]()
+    - [Payload 1 Transfers]()
+    - [Payload 2 Attestations]()
+    - [Payload 3 Contract Controlled Transfers]()
 - [Projects](./projects/summary.md)
     - [Messenger](./projects/messenger/introduction.md)
         - [Prerequistes]()

src/introduction/introduction.md

@@ -4,4 +4,8 @@ Welcome to the xDapp Book and beginning your journey to be a cross-chain develop
 
 For blockchain applications to unlock their true potential, they too must be able to talk to applications on various infrastructure using a common language. These cross chain applications (xDapps) give rise to cross chain data (xData) and cross chain assets (xAssets). With these powerful primitives, blockchain applications can deliver on thier promise of interoperability and composability.  
 
-Ready to step *into the wormhole*?
+Ready to step *into the wormhole*?
+
+---
+Check out the [github respoitory](https://www.github.com/certusone/xdapp-book) of these docs to find the accompaning code in the projects/ directory. 
+