Migrate PWA tutorial starter code repo into amp.dev

## 📖 Missing or Out-of-Date Documentation

### Problem
The [Turn your AMP site into a PWA](https://amp.dev/documentation/guides-and-tutorials/optimize-and-measure/amp_to_pwa/?format=websites) starter [code/lyrical lightning](https://github.com/CrystalOnScript/lyricallyghtning) repo lives under my personal GH account. This needs to be migrated into amp.dev.

### Location
No need to move the existing guide.

### Content type
It might be worth building a more robust demo that we can host somewhere. Also maybe include it in the examples?

### NOTE
I've assigned to myself, but other contributors may take if interested. I'll update this note if I start actively working on this issue if no one has claimed it.