v0.20.0 Structured ICMPv6 Support and no_std PacketBuilder

What's Changed

• Fix docs saying source instead of destination by @vighnesh-sawant in #132
• Update ci jobs by @JulianSchmid in #139
• feat: implement more traits for header types by @thomaseizinger in #138
• Fix lifetime syntax warnings in slices and iterators by @xyzzyz in #137
• Add IpHeadersSlice and IpSlice::header() by @xyzzyz in #136
• Add structured ICMPv6 ND payload and option slice support by @xyzzyz in #140
• Add RFC4443 ICMPv6 payload slice support by @xyzzyz in #141
• Enable PacketBuilder in no_std (alloc/slice) while preserving std API by @xyzzyz in #135
• Increment version to 0.20.0 & resolve newer warnings by @JulianSchmid in #144

New Contributors

• @vighnesh-sawant made their first contribution in #132

Full Changelog: v0.19.0...v0.20.0