User Agent detection and Android/Chromium flow

Source:
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Why?
- to propose in the UI a button "install PWA" when the user agent is Android/Chromium based for an easy setup
- no such thing on iPhone because iOS does not support `beforeinstallprompt` and uses a different flow

Two ways to detect User Agent against a database:
- JavaScript library: [ua-parser-js](https://github.com/faisalman/ua-parser-js)
- Elixir library: [ua_parser](https://github.com/beam-community/ua_parser)

If you use the Elixir library, you must setup:
- a `Plug` to read from the `conn` on the first HTTP pass of the LiveView,
- or use it in the LiveView `mount`or `on_mount` after adding `:user_agent` to the `:connect_info`. Check and .

❓ Browser flow or server flow? With the browser flow, you have more JS to load, 10kB...

Firstyl, let's check `bundlephobia.com`:

Then implement server-side and check