Add an .npmrc

[dinukadesilva]

I am using Pattern Lab Node ccd426e1dcdd7952a8aae2f092fe931e53ba1792 on Windows

Expected Behavior

For the developers, who might have changed the global registry configs, still the patternengine-node-mustache source should be redirected to npm registry when installing node_modules.

Actual Behavior

The npm installation is failed for those who have changed the global npm config.

Steps to Reproduce