Add web wallet example

book/src/SUMMARY.md

@@ -5,6 +5,7 @@
 - [Terminology](terminology.md)
 
 - [Getting Started](getting-started.md)
+  - [Example: Web Wallet](webwallet.md)
 
 - [Programming Model](programs.md)
   - [Example: Tic-Tac-Toe](tictactoe.md)

book/src/webwallet.md

@@ -0,0 +1,13 @@
+# Example app: Web Wallet
+
+## Build and run a web wallet locally
+
+First fetch the example code:
+
+```sh
+$ git clone https://github.com/solana-labs/example-webwallet.git
+$ cd example-webwallet
+```
+
+Next, follow the steps in the git repository's
+[README](https://github.com/solana-labs/example-webwallet/blob/master/README.md).