Fix typo in ping README (#3)

Author: oliver-day

exercises/01.ping/README.mdx

@@ -10,7 +10,7 @@ The Model Context Protocol requires a few things:
 For advanced servers, this communication channel should be two-way, meaning the
 client can send requests, but also receive requests from the server.
 
-In MCP, the client initiates the connection. We're focused on buildig the server
+In MCP, the client initiates the connection. We're focused on building the server
 in this workshop. The client will be the MCP inspector which you can use within
 the workshop app. You can also configure an MCP client of your own if it
 supports the Model Context Protocol we're implementing.