Update changelog

Author: Dr-Emann

CHANGELOG.md

@@ -10,6 +10,11 @@ to [Semantic Versioning][].
 
 ## [Unreleased]
 
+- Use `const fn`s where possible, which allows e.g.
+  `static SPACE: AsciiCharsConst = ascii_chars!(' ');`
+  and `static SUBSTRING: SubstringConst = SubstringConst::new("xyzzy");`
+- Trait bounds removed from generic types, bounds are only required for impls
+
 ## [0.5.3] - 2022-07-06
 
 - Fix buffer overflows in find. (#55)