Update CHANGELOG for v1.0.0

***NO_CI***

Author: nfbot

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## [v1.0.0-preview.12](https://github.com/nanoframework/System.IO.Ports/tree/v1.0.0-preview.12) (2021-05-24)
+
+[Full Changelog](https://github.com/nanoframework/System.IO.Ports/compare/e3fcbb11188271f15c64109194b016f944569597...v1.0.0-preview.12)
+
 
 
 \* *This Changelog was automatically generated by [github_changelog_generator](https://github.com/github-changelog-generator/github-changelog-generator)*