Added npm-run-all module so 'npm run watch' command can work without extra work

[SachinMali]

Description

Added npm-run-all module so 'npm run watch' command can work without extra work

Related Issue

Please see adobe/aem-guides-wknd#343 and #941

Motivation and Context

The Client-Side Libraries topic and associated steps are seamless and relevant.

How Has This Been Tested?

On local AEM project creates using archetype-39 and installing 'npm-run-all' and running the 'npm run watch' command, on Node 16.18.1

Screenshots (if appropriate):

Types of changes

• [x ] Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• [x ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x ] I have signed the Adobe Open Source CLA.
• [x ] My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• [x ] I have read the CONTRIBUTING document.
• [x ] I have added tests to cover my changes.
• [x ] All new and existing tests passed.