Add CODEOWNERS (#76)

* Add CODEOWNERS

* remove deprecated lint

Release v0.3.0 (#49)

* Release v0.3.0

* update the CHANGELOG

* add the PR template

* update no_std check in CI

use `aarch64-unknown-none` env instead

* separate the benches

Co-authored-by: Tom Shen <tomshen@berkeley.edu>