Improved support for VSCode #region code folding in html sections

[axwalker]

Is your feature request related to a problem? Please describe.
Region folding was added for Svelte files but from what I can tell it only works for JS comments, eg //#region. This works fine within the <script> tag but is problematic within the html section of a Svelte component. You can still use //#region there but then that actually gets rendered in your HTML because it's not an HTML comment.

Describe the solution you'd like
Also support regions defined with html comments: eg <!--#region-->/<!--#endregion-->

Additional context
Related closed issue: #525

[dummdidumm]

Seems vs code implemented it for html in this commit microsoft/vscode@4f9f4eb, maybe we can do something similar