Make Composer available via npm run on host machine

[paulbonneau]

Context

Working on a ticket on my wordpress-develop cloned instance, I wanted to lint and format my code but :

• I couldn't find the command in composer.json in order to do so;
• I didn't want to install composer nor phpcs on my host machine because those tools are already available in the container spawned.

##Solutions
To lint my code I used this command : node ./tools/local-env/scripts/docker.js run -T --rm php composer lint [my_file]

@SirLouen suggested to create a new custom script in package.json enabling developers to directly invoke the composer instance of the wordpressdevelop/php container from their host machine. Implementing this will simplifies future call to composer specific scripts from host machine (linting, formating etc ...).

Trac ticket: (https://core.trac.wordpress.org/ticket/63912)

[github-actions]

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Props paulbonneau.

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[github-actions]

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[github-actions]

A commit was made that fixes the Trac ticket referenced in the description of this pull request.

SVN changeset: 60803
GitHub commit: bbc90ae

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.