Requiring users to append 'px' to react native units should be a linter preference and should not be done by this plugin

[shamilovtim]

In v5.0.0-rc.0 this plugin has decided unilaterally and without much conversation that react native developers should be forced to append 'px' on their units. That is the job for a linter and it is a personal preference -- it is not the domain of this plugin. I appreciate the work everyone does here but I should not have other people's style decisions enforced over my code.

Please see https://facebook.github.io/react-native/docs/style. React Native units are unitless. Until the RN team decides otherwise this plugin is forcing devs to both write 'px' in styled-components and not write 'px' in vanilla RN components. That's messy and should not be the case.

Please provide a path for people to continue using unitless styles whether it be as a global setting or otherwise.

[jacobp100]

Please see #40 and surrounding discussions