Add `styled-components` version

[matteocng]

Add styled-components version of FlagIcon. It should be built using StyledFlagIconFactory and support theming (e.g custom flags).

// ES2015 version.
import StyledFlagIconFactory from 'react-flag-icon-css/module/styled'
// Legacy CommonJS version.
import StyledFlagIconFactory from 'react-flag-icon-css/lib/styled'

[evert-smit]

Hi, I was wondering, is there some more info on a possible styled-components version?

[matteocng]

Hi @evert-smit it is unlikely I can release the SC version soon, but I will reference this thread when that happens.