Add 'npm run-script build' mentioned in the README.md

[marcofranssen]

This resolves #105

[msftclas]

All CLA requirements met.

[msftclas]

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[jeffwilcox]

Odd that the CLA didn't function well here... I merged after review, then saw the CLA status was red, but yet, it's also green. I'm trying to undo the revert now :)