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:

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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.

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[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.