Build/Test Tools: Make Composer available via npm run on the host machine.

This enables developers to directly invoke the Composer instance of the `wordpressdevelop/php` container from their host machine, making it easier to call Composer-specific scripts: linting, formatting, etc.

Props paulbonneau, SirLouen.
Fixes #63912.

git-svn-id: https://develop.svn.wordpress.org/trunk@60803 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

package.json

@@ -184,6 +184,7 @@
 		"env:reset": "node ./tools/local-env/scripts/docker.js down --rmi all -v --remove-orphans",
 		"env:install": "node ./tools/local-env/scripts/install.js",
 		"env:cli": "node ./tools/local-env/scripts/docker.js exec --user wp_php cli wp",
+		"env:composer": "node ./tools/local-env/scripts/docker.js run -T --rm php composer",
 		"env:logs": "node ./tools/local-env/scripts/docker.js logs",
 		"env:pull": "node ./tools/local-env/scripts/docker.js pull",
 		"test:performance": "wp-scripts test-playwright --config tests/performance/playwright.config.js",