Function web_get_content_async 

pub async fn web_get_content_async(
    url: &str,
    proxy_config: &ProxyConfig,
    headers: Option<&HashMap<CaseInsensitiveString, String>>,
) -> Result<String, String>

Asynchronous function that returns only the body content if status is 2xx, otherwise treats as error This provides backward compatibility with code expecting only successful responses