docs(README.md): add note about compiling with --release to ensure timing-sensitive code is correct

Author: reivilibre

README.md

@@ -18,6 +18,11 @@ The only prerequisites are an embedded-hal implementation that provides:
 See the [stm32f042 example](examples/stm32f042.rs) for a commented example of
 how to use the library.
 
+### Release mode may be required
+
+Compiling in debug mode may disturb the timing-sensitive parts of this crate and ultimately lead to failure.
+In this case, you will likely receive a `Timeout` error. Try compiling with `--release` instead.
+
 ### Tests
 
 To run the tests, use something like `cargo test --lib --target x86_64-unknown-linux-gnu`.