Add 7.0.0 to CHANGELOG

[ci skip]

Author: mmoll

CHANGELOG.md

@@ -3,6 +3,19 @@
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [7.0.0] - 2021-04-22
+### Added
+- Add PHP 8.0 support
+- Add `Generic.WhiteSpace.ArbitraryParenthesesSpacing`
+- Add `Squiz.PHP.DisallowMultipleAssignments`
+- Add `SlevomatCodingStandard.Arrays.SingleLineArrayWhitespace`
+- Add `SlevomatCodingStandard.Namespaces.ReferenceUsedNamesOnly`
+- Add `SlevomatCodingStandard.Functions.UnusedParameter`
+- Add `SlevomatCodingStandard.Functions.UselessParameterDefaultValue`
+### Changed
+-  Raised minimum PHPCS release
+-  Raised minimum Slevomat CS release
+
 ## [6.0.0] - 2020-10-29
 ### Added
 - Add `SlevomatCodingStandard.Classes.DisallowMultiConstantDefinition`