''' 
 <div className="col-lg-6 row-item">
          <div className="file-upload-arrow">
            <img src={FileArrowIcon} alt="File Upload Arrow Icon" />
          </div>
          <div className="file-upload-text">
            Drag and drop document here to upload
          </div>
          <div className="file-attach-instructions">
            Please attach the file(s) below (use the Add button). We recommend using A4-size PDF, BMP, PNG, DOC, DOCX, JPG and JPEG files. File size cannot be more than 20 megabytes (MB). Your files will be uploaded when you submit your form.
          </div>
          <div className="file-add-button">
            <button onClick={addFileHandler}>Add File</button>
          </div>
        </div>
   '''
 
 Your are a senior react developer.
 
 I want you to implement a functionality to upload files on button click event and drag and drop.
 
 Contrainst:
 
1. function should be implemented on `addFileHandler` event given above.
2. File can also be uploaded by drag and drop into row-item div element.
3. instructions for file upload is given `file-attach-instructions` div element.
4. You can use packages like `react-uploader` to implement this.
5. Finally return the updated version of code. Current code is above for reference.