Note about nightly Rust

README.md

@@ -5,6 +5,8 @@ A simple attempt at a `#[no_std]` compatible allocator that can track
 allocations on a per-thread basis, for the purpose of guaranteeing that
 performance-critical code doesn't trigger an allocation while running.
 
+Nightly Rust is required because of a dependence on the `alloc` crate.
+
 The current state has all the infrastructure in place, but the tests are a bit
 flaky. As such, this crate likely won't see much further development; if you
 are interested in claiming the qadapt name, please reach out to the author