Prepare the v3.3.0 release (#37)

Introducing a CHANGELOG file to keep track of all modifications. It will
be used when performing the releases @ github to fill-in the details
there.

Author: stronk7

CHANGELOG.md

@@ -0,0 +1,33 @@
+# Change log
+
+All notable changes to this project will be documented in this file.
+This project adheres to [Semantic Versioning](http://semver.org/).
+
+The format of this change log follows the advice given at [Keep a CHANGELOG](http://keepachangelog.com).
+
+## [Unreleased]
+
+## [v3.3.0] - 2023-01-13
+### Added
+- Enforce the use of `&&` and `||` logical operators, warning about `and` and `or`: `Squiz.Operators.ValidLogicalOperators`
+
+### Changed
+- Many internal changes towards better self-testing and integration with other tools ([GH workflows](https://github.com/moodlehq/moodle-cs/actions), codechecker, core, phpunit...).
+- Upgraded the [PHPCompatibility standard](https://github.com/PHPCompatibility/PHPCompatibility) from 3 years old version 9.3.5 (no releases since then) to current development version.
+
+### Fixed
+- Stop considering `class_alias` like a side effect.
+- Add back the `Squiz.Arrays.ArrayBracketSpacing` sniff.
+
+## v3.2.0 - 2022-02-28
+This release is the first release of the new [moodlehq/moodle-cs](https://packagist.org/packages/moodlehq/moodle-plugin-ci) packages.
+
+These rules, in an identical form, were previously available as a part of the [local_codechecker Moodle plugin](https://moodle.org/plugins/local_codechecker)  but are being moved to their own repository to make installation friendlier for developers.
+
+All features are maintained and no new features have been introduced to either the rules, or the sniffs.
+
+All the details about [previous releases] can be found in [local_codechecker](https://github.com/moodlehq/moodle-local_codechecker) own change log.
+
+[Unreleased]: https://github.com/moodlehq/moodle-cs/compare/v3.3.0...main
+[v3.3.0]: https://github.com/moodlehq/moodle-cs/compare/v3.2.0...v3.3.0
+[Previous releases]: https://github.com/moodlehq/moodle-local_codechecker/blob/master/CHANGES.md#changes-in-version-400-20220825---welcome-moodle-cs