add phpcs check with Magento Coding Standard to CI

[smoucka]

Description

Fixes Magento Coding Standard failures in phtml template files.

Adds a blocking CI check that runs phpcs with the Magento Coding Standard (see screenshot below for sample failure). Note this only alerts on severity=10 which is the same as the Magento Marketplace automated technical review. Had to add a separate composer file for this particular CI check because it's incompatible with the dev-develop branch of the PHPCompatibliity tool which is the only way we can get the ongoing maintenance for php 8 compatibility checks.

Manual Testing Steps

Failure

Pre-Submission Checklist:

• You've updated the CHANGELOG following the steps here
• Internal Only - If this is a release, please confirm the following:
  • The links in the changelog have been updated to point towards the new versions
  • The version has been incremented in the following places: module.xml and composer.json

NOTE: Please use the Changelogger cli tool to manage versioned file upgrades.

[zchenk]

👍