v0.5.0

This release adopts hpke 0.10.0, which no longer pins a specific version of zeroize.

What's Changed

• Update hpke requirement from 0.9.0 to 0.10.0 by @dependabot in #19
• Release crate and package version 0.5.0 by @tgeoghegan in #20

Full Changelog: v0.4.0...v0.5.0