docs(README): add 173app to the built with list

[Carrotzpc]

add https://173app.com to the built with list

[welcome]

💖 Thanks for opening this pull request! 💖

Here is a list of things that will help get it across the finish line:

• Run yarn lint locally to catch formatting errors. This will fix some errors automatically, commit and push any changes.
• Run yarn test locally to catch errors. This ensures all components still behave as they should.
• Run yarn start to run the doc site locally and try a few pages, ensuring everything is in good working order.
• Include tests when adding/changing behavior.

We get a lot of pull requests on this repo, so please be patient and we will get back to you as soon as we can.

[levithomason]

It seems the CDN is not responding for this app. I'm in the US, west coast. Does it work for you?

[Carrotzpc]

@levithomason Yes, it work for me in China. And I test the CDN in the US, Los Angeles by VPN, it can work but slowly.

[welcome]

Congrats on merging your first pull request! 🎉🎉🎉

[levithomason]

❤️

[levithomason]

Released in [email protected].

[Carrotzpc]

👍 @levithomason