ng-add schematic should optionally setup npm publish

[yjaaidi]

ng-add schematic should prompt user about setting up npm publish if project is publishable. If user accepts, schematic should:

• [ ] add a deploy target using ngx-deploy-npm
• [ ] add a deploy target using @jscutlery/semver:github
• [ ] add the target to postTargets (cf. #167)

[dianjuar]

Hello @yjaaidi and @edbzn.

I'm ngx-deploy-npm's author. If there is anything I can help/adapt in my tool to help you support this, let me know 👍 . DM's are open.