feature: handle command arguments with spaces

[erezrokah]

Which problem is this feature request solving?

At the moment we return a dev/build command as a single string, e.g. npm run <some-script>.
This might cause issues if <some-script> contains spaces.
We should support this use case.

Related to netlify/cli#2857 (comment)

Describe the solution you'd like

Handle spaces in command arguments, via quoting the arguments or escaping the spaces.

Describe alternatives you've considered

N/A

Can you submit a pull request?

Yes