feat: expose wry permission handler API

[F0RLE]

Is your feature request related to a problem? Please describe.

Currently, Tauri applications (especially on Windows/WebView2) show native permission prompts for capabilities like Microphone and Camera. For kiosk applications or embedded systems where user interaction is limited, we need a way to automatically grant these permissions without prompting the user.

Describe the solution you'd like

Since wry has recently added a with_permission_handler API (supported in tauri-apps/wry#1656), I would like to see this exposed in Tauri.

Ideally, we could configure a handler in WebviewWindowBuilder similar to how navigation_handler is exposed:

tauri::Builder::default()
  .setup(|app| {
    let window = tauri::WebviewWindowBuilder::new(app, "main", tauri::WebviewUrl::default())
      .permission_handler(|kind| {
        match kind {
           // Allow microphone access without prompt
           tauri::PermissionKind::Microphone => tauri::PermissionResponse::Allow,
           _ => tauri::PermissionResponse::Default,
        }
      })
      .build()?;
    Ok(())
  })