update changelog

Author: vincentsarago

Diff for: CHANGELOG.txt

@@ -4,6 +4,7 @@
 - Rename `stac_pydantic.api.conformance.ConformanceClasses` to `stac_pydantic.api.conformance.Conformance`
 - Update pre-commit configuration and switch to astral-sh/ruff for linter and formater
 - Add official support for python 3.12
+- Enforce required `type` key for `Collection` and `Catalog` models
 
 3.0.0 (2024-01-25)
 ------------------