Share folder with user once they fill out a Google form

Code.gs

/*

1. Open or create your form.
2. Click the wheel icon, check "Collect email addresses", save. This will automatically get the email from the user.
  * In the survey, you should probably put some text that explains that it will automatically use their account's email.
3. Click the three dots in the top right, select "Script Editor."
4. Copy this entire file and paste it in the editor.
5. Replace your_folder_id with your folder ID.
  * To find the folder ID, open the folder you wish to share on the web.
  * In the address bar, it should be something like https://drive.google.com/drive/u/0/folders/0B1jVrClv_7PllGlxTz4YjXRCeFk
  * 0B1jVrClv_7PllGlxTz4YjXRCeFk is your folder ID.
6. Make sure the script looks alright.
7. Select Edit > Current project's triggers from the toolbar. You might need to name the project.
8. Click "Click here to add one now." to add a trigger.
9. Add a trigger:
  * Run: addNewUser
  * Events: From form, On form submit
10. Save. Name the project if needed. Review Permissions:
  * Choose your account if needed.
  * There is a safety warning since you wrote the script yourself.
  * Click "Advanced" in the bottom left.
  * Trust, click "Go to Untitled project (unsafe)."
  * Type continue in the textbox if needed.
  * Click "Allow."
11. You're done!

*/

function addNewUser(e) {
  var email = e.response.getRespondentEmail();
  var sheet = DriveApp.getFolderById("your_folder_id");
  sheet.addEditor(email);
}