Update changelog

Author: hannobraun

CHANGELOG.md

@@ -1,3 +1,12 @@
+### v0.5.0 (2021-03-02)
+
+- Use `byte` crate instead of `bytes` for encoding/decoding ([#35])
+- Fix accidental dependence on `alloc` ([#35])
+- Fix crate not compiling on thumbv6m targets ([#35])
+
+[#35]: https://github.com/braun-embedded/rust-ieee802.15.4/pull/35
+
+
 ### v0.4.0 (2020-09-15)
 
 - Fix panic when encoding frame header ([#26])