GitHub actions revised

[ashryanbeats]

Description

• [action] Now running jobs on Mac and Win
• [action] Ensuring xdpm install action doesn't fail due to non-existent target dirs by using mkdir/md
• [lib/validate.js] Ensuring xdpm validate action doesn't fail by checking if .icons property existing before invoking .forEach

Related Issue

AdobeXD#35

Motivation and Context

Trying to ensure we don't end up with pesky failure annotations in our actions results when we actually intend for the action to fail.

Types of changes

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

Checklist:

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

[pklaschka]

This is great 👍