static ReadableMap getCancelMap() {
        WritableMap map = Arguments.createMap();
        map.putBoolean("didCancel", true);
        return map;
    }
Verifies the content typs of a file URI. A helper function
for isVideoType and isImageType

@param contentMimeType - "video/" or "image/"
@param uri             - file uri
@param context         - react context
@return a boolean to determine if file is of specified content type i.e. image or video
android/src/main/java/com/imagepicker/Utils.java