Embed webview if not available

[bumi]

This embeds the webview dependency which will be used if the webview is not available. Otherwise the user would get prompted to download it and I thought this is easier.

https://wails.io/docs/guides/windows/

[rdmitr]

If I understand the docs correctly, this option doesn’t embed Webview itself; it only embeds the bootstrapper that still prompts the users to download Webview. But it can be a bit more straightforward, I guess