Submit to Amazon Appstore for Fire tablets

**NEEDS USER ACTION** — requires Amazon Developer Account (free).

Amazon Fire tablets are the #1 kids' tablet.

**Steps:**
- User creates Amazon Developer account (free)
- Reuse the Android APK from Capacitor
- Create listing with same materials
- Submit

Very similar to Google Play process.

**Acceptance criteria:**
- [ ] App published on Amazon Appstore