docs: add Juno to Trusted by (#1473)

## Summary

- Add Juno to the homepage Trusted by list.
- Use the public App Store icon and listing URL.
- Scope the alt text to the Juno text chat app use case.

## Validation

- `git diff --check`
- `npx --yes prettier@2.8.8 --check docs/src/pages/index.tsx`