Add official support for node 11

[Fatme]

Is your feature request related to a problem? Please describe.

NativeScript CLI shows an warning Support for Node.js 11.6.0 is not verified. NativeScript CLI might not install or run properly. when it is used with node v11.6.0.
The user is not able to install NativeScript CLI with node v11.6.0 due to The engine "node" is incompatible with this module. Expected version ">=8.0.0 <11.0.0". Got "11.6.0"

Describe the solution you'd like
Implemented in #4303

Describe alternatives you've considered

Additional context