Composer: prevent a lock file from being created

Composer 1.10.0 introduced a `lock` config option, which, when set to `false` will prevent a `composer.lock` file from being created and will ignore it when one exists.

This is a useful option for libraries such as this where the `lock` file has no meaning.

It also makes life easier for contributors as they don't have to remember that for this repo they should use `composer update` instead of `composer install`. Both will now work the same.

Refs:
https://getcomposer.org/doc/06-config.md#lock

.github/workflows/quicktest.yml

@@ -51,6 +51,10 @@ jobs:
           ini-values: error_reporting=E_ALL & ~E_DEPRECATED, display_errors=On
           coverage: none
 
+      - name: Enable creation of `composer.lock` file
+        if: ${{ matrix.dependencies == 'lowest' }}
+        run: composer config --unset lock
+
       # Install dependencies and handle caching in one go.
       # @link https://github.com/marketplace/actions/install-php-dependencies-with-composer
       - name: Install Composer dependencies

.github/workflows/test.yml

@@ -123,6 +123,10 @@ jobs:
           sirbrillig/phpcs-variable-analysis:"2.x"
           wp-coding-standards/wpcs:"dev-develop"
 
+      - name: Enable creation of `composer.lock` file
+        if: ${{ matrix.dependencies == 'lowest' }}
+        run: composer config --unset lock
+
       # Install dependencies and handle caching in one go.
       # @link https://github.com/marketplace/actions/install-php-dependencies-with-composer
       - name: Install Composer dependencies

composer.json

@@ -33,7 +33,8 @@
 	"config": {
 		"allow-plugins": {
 			"dealerdirect/phpcodesniffer-composer-installer": true
-		}
+		},
+		"lock": false
 	},
 	"scripts": {
 		"test-ruleset": "bin/ruleset-tests",