feat: add CHANGELOG for 1.0.0 release

Author: spbsoluble

CHANGELOG.md

@@ -0,0 +1,13 @@
+# Changelog
+
+## [1.0.0] - Unreleased
+
+### Added
+
+- Initial release of the CERTInext AnyCA REST Gateway plugin
+- Certificate enrollment for DV SSL (838), DV Wildcard (839), DV UCC (840), OV SSL (842), and EV SSL (846) product types
+- Certificate revocation via `RevokeOrder` with RFC 5280 reason code mapping
+- Full and incremental CA synchronization via paginated `GetOrderReport`
+- AccessKey (HMAC-SHA256) and OAuth client credentials authentication modes
+- `IgnoreExpired` flag to exclude expired certificates from synchronization
+- Live integration tests covering all supported SSL/TLS product types (draft order mode)