Clarify test location

I was confused (briefly) about where the tests were located. Perhaps this language is clearer?

contracts/README.md

@@ -6,7 +6,7 @@ There are two primary starter template contracts included.
 The Solidity libraries for Bonsai can be found at [github.com/risc0/risc0](https://github.com/risc0/risc0/tree/main/bonsai/ethereum).
 
 Contracts are built and tested with [forge], which is part of the [Foundry] toolkit.
-Tests are defined in the `tests` directory.
+Tests are defined in the `tests` directory in the root of this template.
 
 [Foundry]: https://getfoundry.sh/
 [forge]: https://github.com/foundry-rs/foundry#forge