Ask About HtmlTextWriter

## Summary

Our repo uses `HtmlTextWriter` which is not supported by ASP.NetCore and this adapters.
I want to ask if there is equivalent and if there is plan to add them to adapter.

## Motivation and goals

We need migrate code (an API in Sharepoint) to ASP.NetCore and we find that the APIs are not supported by ASP.NetCore.

## In scope

`HtmlTextWriter`

I only found a 3rd-party package [HtmlTextWriter](https://www.nuget.org/packages/HtmlTextWriter)
Is there a plan to add HtmlTextWriter into adapters?

## Examples
Use HtmlTextWriter to encode url
```C#
HtmlTextWriter writer = new HtmlTextWriter(new StringWriter(new StringBuilder(), CultureInfo.InvariantCulture));
writer.Write(url)
```