Set packageName in TypeScript reference file

[devloco]

This PR is sent as suggested by @Timer here:
#5811

Here are the full steps that I used to test:

1. I published my react-scripts changes to NPM as @devloco/react-scripts-test
2. bash prompt at: create-react-app/packages/create-react-app
3. npm link (to pick up the changes made to createReactApp.js)
4. cd ~/temp
5. create-react-app foo1 --typescript --scripts-version @devloco/react-scripts-test
6. See app creation succeed.
7. cd foo1/src
8. vim react-app-env.d.ts
9. See that "types" prop value is @devloco/react-scripts-test
10. :q! + ENTER to exit vim
11. yarn start
12. See no errors happen. Webpack Dev Server and browser tab launch successfully. Page renders in browser as usual.

Screenshots:

---

Make sure that not using --scripts-version still works the same

1. cd ~/temp
2. `create-react-app foo2 --typescript
3. See app creation succeed.
4. cd foo2/src
5. vim react-app-env.d.ts
6. See that "types" prop value is react-scripts
7. :q! + ENTER to exit vim
8. yarn start
9. See no errors happen. Webpack Dev Server and browser tab launch successfully. Page renders in browser as usual.

[facebook-github-bot]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. In order for us to review and merge your code, please sign up at https://code.facebook.com/cla. If you are contributing on behalf of someone else (eg your employer), the individual CLA may not be sufficient and your employer may need the corporate CLA signed.

If you have received this in error or have any questions, please contact us at cla@fb.com. Thanks!

[facebook-github-bot]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Facebook open source project. Thanks!

[Timer]

Hmm, this would break existing apps adding TypeScript. We just need to parse it from paths.ownPackageJson.

[mrmckeb]

@Timer This is included in this #5877, along with another fix.