Source-file copyright and license notices, preserved verbatim.

===== src/fft/mod.rs (source SHA-256 33249eec851455d9525cfa848cd3246ac42cd84adc177af4ce54535ca30751e3) =====
//! From https://gitlab.com/teskje/microfft-rs
//! Copyright (c) 2020-2024 Jan Teske, MIT license
//!
//! This is actually 2.5x slower than realfft/rustfft, but it's much simpler and doesn't require `std`.
//! Still, it only takes ~1.8us - only slightly slower than the first NN layer.
