Kathryn Long

F16C hardware intrinsics still not stabilized, just needs stabilization PR https://github.com/rust-lang/stdarch/issues/1234 Probably the biggest priority for crate now that `const` conversions are done.

Current implementation uses `mem::transmute` which is not ideal. Awaiting stabilization of https://github.com/rust-lang/rust/issues/57241 which is blocked by general Rust float soundess discussions.

Github Actions CI now runs i686 and aarch64 builds like it used to, but no tests are being run for i686. Use CircleCI to do this like is being done...

Add vector arithmetic operations on slices/arrays of `f16`, that can utilize SIMD hardware when available, like is already done for conversions.

Add support for the new [AVX-512-BF16](https://en.wikipedia.org/wiki/AVX-512#BF16) x86 extension for `bf16` conversions. Will need to be added to core::arch. Extension intrinsic docs: https://www.intel.com/content/www/us/en/develop/documentation/cpp-compiler-developer-guide-and-reference/top/compiler-reference/intrinsics/intrinsics-for-avx-512-bf16-instructions.html

Add support for the new [AVX-512-FP16](https://en.wikipedia.org/wiki/AVX-512#FP16) x86 extension, ~~which appears to already be available as unstable in `core::arch`~~. It allows for a wide variety of operations. Will need to be...

Allow selecting how to round when converting down to `f16`. Note that while x86 F16C hardware allows selecting rounding mode, ARM in particular does not, so keeping consistent across implementation...

Expose an `[f16; 4]` (and `[f16; 8]`, see #66) API in addition to the slice convenience traits.