static @Nullable String getMimeTypeForContent(Uri uri, Context context) {
        String fileName = getFileNameForContent(uri, context);
        String fileType = "Unknown";

        int lastDotIndex = fileName.lastIndexOf('.');
        if (lastDotIndex != -1) {
            fileType = fileName.substring(lastDotIndex + 1);
        }
        return fileType;
    }
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