solana: Add build prerequisites to README

If the toolchain is not configured properly on the local machine, the
code will fail to build and run and will emit only very cryptic errors.

Author: johnsaigle

solana/README.md

@@ -1,4 +1,19 @@
-# Message Lifecycle (Solana)
+# Solana 
+
+## Prequisities
+
+Ensure that you are using the correct version of the Solana and Anchor CLI tools by consulting `Anchor.toml`.
+```toml
+[toolchain]
+anchor_version = "0.29.0"   # CLI
+solana_version = "1.17.2"
+```
+
+You will also need to install the toolchain listed in `rust-toolchain`.
+
+## Design Overview
+
+### Message Lifecycle (Solana)
 
 1. **Transfer**