preview

feat(gui, tauri): Accept --testnet flag, default to mainnet (#106)

This PR tackles #92 

- Add the `tauri-plugin-cli` (only on desktop)
- Check in the frontend if the `--testnet` flag is set. If it's set we pass `testnet=true` to the `initialize_context` command on invokation
- We add the `vite-plugin-top-level-await` to allow top level await in all browsers
- Remove the `bitcoin_confirmation_target` from settings for simplicity