rm unused ImageArtifactType

src/core/ImageArtifactType.js

@@ -1,19 +0,0 @@
-class ImageArtifactType {
-	constructor() {
-		throw new Error('Cannot create instance of ImageArtifactType')
-	}
-}
-
-ImageArtifactType.SMALL = 'small'
-ImageArtifactType.MEDIUM = 'medium'
-ImageArtifactType.BIG = 'big'
-ImageArtifactType.LARGE = 'large'
-ImageArtifactType.ORIGIN = 'original'
-ImageArtifactType.ORIGINAL = 'original'
-
-ImageArtifactType.FACEBOOK = 'fb'
-
-ImageArtifactType.RETINA_DENSITY = 2
-ImageArtifactType.retina = type => `${type}@${ImageArtifactType.RETINA_DENSITY}`
-
-module.exports = ImageArtifactType