Add body_text and body_html to Comment model

[pnevyk]

The models::pulls::Comment struct is used for example here. If I simulate the request with GitHub CLI

gh api \
  -H "Accept: application/vnd.github.full+json" \
  -H "X-GitHub-Api-Version: 2022-11-28" \
  /repos/XAMPPRocky/octocrab/pulls/comments/426219964

I get

{
    // ...
    "body": "I'd remove the error path, and change the return type to `Result<models::User>`. I'd consider it programmer error to use the `CurrentAuthHandler` when using a token that doesn't have an authenticated user behind it. And people who need to handle it will get an error anyway.",
    // ...
    "body_html": "<p dir=\"auto\">I'd remove the error path, and change the return type to <code class=\"notranslate\">Result&lt;models::User&gt;</code>. I'd consider it programmer error to use the <code class=\"notranslate\">CurrentAuthHandler</code> when using a token that doesn't have an authenticated user behind it. And people who need to handle it will get an error anyway.</p>",
    "body_text": "I'd remove the error path, and change the return type to Result<models::User>. I'd consider it programmer error to use the CurrentAuthHandler when using a token that doesn't have an authenticated user behind it. And people who need to handle it will get an error anyway.",
    // ...
}

This PR adds missing body_text and body_html.