[html] propose `charset="UTF-8"` `target="_blank"` and `rel="stylesheet"`

<!-- ⚠️⚠️ Do Not Delete This! feature_request_template ⚠️⚠️ --> <!-- Please read our Rules of Conduct: https://opensource.microsoft.com/codeofconduct/ --> <!-- Please search existing issues to avoid creating duplicates. --> <!-- Describe the feature you'd like. --> Some attribute values like `charset="UTF-8"` , `target="_blank"` or `rel="stylesheet"` doesn't give me suggestions but other text editors that I've tried do. Is there an extension for this ? Or is this a problem with my version of vscode ? > VSCode Version: 1.58.1 > OS: Windows 10 Latest Verion