Update bit.ly PWA links. #5497

[loganasherjones]

This update fixes issue #5497 and points to the correct documentation page.

http://bit.ly/CRA-PWA2 => https://facebook.github.io/create-react-app/docs/making-a-progressive-web-app

I'm happy to give over control of the bit.ly link (if that is a thing I can do)

If you'd prefer to find the original owner, and have them change it, feel free to close this PR.

[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 # 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]

All of these links exist in already-created projects, so we'd like to find the original author and ask them to update the link (if possible).

[bugzpodder]

#3872
@bondz

[loganasherjones]

Sounds good!