Add an option for adding NODE_ENV checks for minifiers

[sohkai]

Consumers of a library should be able to access the library's proptypes in dev builds, but then be able to seamlessly strip them out for production.

See conversation on https://github.com/brigand/babel-plugin-flow-react-proptypes/issues/70#issuecomment-278551711.

TODO:

• [x] add deadCode config option (see readme)
• [x] dce for the propTypes object
• [x] dce for exported types (export type Foo =)
• [ ] dce for imported types (import type {Foo} from './Foo)
• [ ] dce for the actual 'propTypes' property, both with the default assignment at end of file, and the the useStatic option (currently propTypes=null after minify)

[dlebedynskyi]

Hi, tried dead code and running into issues with deadCode: true

Error: Error: No substitution given for "NODE_ENV". If this is not meant to be a
            placeholder you may want to consider passing one of the following options to @babel/template:
            - { placeholderPattern: false, placeholderWhitelist: new Set(['NODE_ENV'])}
            - { placeholderPattern: /^NODE_ENV$/ }

any suggestion on fix?

[brigand]

@dlebedynskyi Thanks for the report, should be fixed in 24.1.2

[dlebedynskyi]

@brigand confirmed, working now. Thank you