Composer: update PHPCS Composer plugin dependency

The DealerDirect Composer plugin has just released version `0.7.0`.
As Composer treats minors < 1.0 as majors, updating to this version requires an update to the `composer.json` requirements.

> For pre-1.0 versions it also acts with safety in mind and treats `^0.3` as `>=0.3.0 <0.4.0`.

Refs:
* https://github.com/Dealerdirect/phpcodesniffer-composer-installer/releases/tag/v0.7.0
* https://getcomposer.org/doc/articles/versions.md#caret-version-range-

Author: jrfnl

CHANGELOG.md

@@ -10,7 +10,7 @@ This projects adheres to [Keep a CHANGELOG](http://keepachangelog.com/) and uses
 _Nothing yet._
 
 
-## [1.0.0-alpha3] - 2020-06-14
+## [1.0.0-alpha3] - 2020-06-29
 
 Notes:
 * While still in alpha, some BC-breaks may be introduced. These are clearly indicated in the changelog with the :warning: symbol.
@@ -86,6 +86,7 @@ Notes:
 
 #### Other
 * Composer: PHPCSUtils can now be installed in combination with PHPCS `4.0.x-dev@dev` for testing purposes.
+* Composer: The version requirements for the [DealerDirect Composer PHPCS plugin] have been widened to allow for version 0.7.0 which supports Composer 2.0.0.
 * Readme/website homepage: textual improvements. Props [@GaryJones]. [#121](https://github.com/PHPCSStandards/PHPCSUtils/pull/121)
 * Readme/website homepage: added additional FAQ question & answers. [#157](https://github.com/PHPCSStandards/PHPCSUtils/pull/157)
 * The website homepage is now generated using the GitHub Pages gem with Jekyll, making maintenance easier. [#141](https://github.com/PHPCSStandards/PHPCSUtils/pull/141)

composer.json

@@ -24,7 +24,7 @@
     "require" : {
         "php" : ">=5.4",
         "squizlabs/php_codesniffer" : "^2.6.0 || ^3.1.0 || 4.0.x-dev@dev",
-        "dealerdirect/phpcodesniffer-composer-installer" : "^0.4.1 || ^0.5 || ^0.6.2"
+        "dealerdirect/phpcodesniffer-composer-installer" : "^0.4.1 || ^0.5 || ^0.6.2 || ^0.7"
     },
     "require-dev" : {
         "php-parallel-lint/php-parallel-lint": "^1.1.0",