Incomplete documentation for cs/web/broad-cookie-domain

I believe the CodeQL documentation here conflicts with MDN by omission:
> In this example cookie1 is accessible from online-bank.com ...
> ```
> HttpCookie cookie1 = new HttpCookie("sessionID");
> cookie1.Domain = "online-bank.com";
> ```

https://codeql.github.com/codeql-query-help/csharp/cs-web-broad-cookie-domain/

According to MDN, that cookie would _also_ be available to subdomains:
> For example, if you set Domain=mozilla.org, cookies are available on mozilla.org and its subdomains like developer.mozilla.org.

https://developer.mozilla.org/en-US/docs/Web/HTTP/Cookies#domain_attribute

The CodeQL documentation should state that "In this example cookie1 is accessible from online-bank.com _and its subdomains_".

Open the CodeQL documentation page for cs/web/broad-cookie-domain and compare its cookie-domain wording with the linked MDN guidance. Update the example description to mention online-bank.com and its subdomains, then check that the rendered page and references remain accurate.

Written by the indexing model from the issue text.