[API Proposal]: Add StringBuilder overload for WebUtility.HtmlEncode

[Lanayx]

Background and motivation

I suggest adding StringBuilder overloads in WebUtility similar to TextWriter one. Actually one very similar already exists for private implementation.

Motivation: in Oxpecker framework (which is currently one of the top frameworks at Techempower benchmarks) I'm using StringBuilder for ViewEngine rather than TextWriter because it gives about 10% performance increase for rendering HTML views to string. One downside is that HtmlEncode method doesn't allow for StringBuilder, so I'm allocating strings each time encoding is required.
If overload is added, it can behave faster than TextWriter since no intermediate ValueStringBuilder instances are requried.

API Proposal

public static class WebUtility
{
    public static void HtmlEncode(string? value, StringBuilder output)
    public static void HtmlDecode(string? value, StringBuilder output)
}

API Usage

var sb = new StringBuilder();
WebUtility.HtmlEncode("myString", sb);

Alternative Designs

No response

Risks

No response

[Lanayx]

@timcassel Yes, I'm aware of this type, but as I said - using it gives 10% overhead in my benchmarks compared to straight StringBuilder usage. With implemented, overload with StringBuilder will give performance difference even larger (due to aforementioned possibility of getting rid of intermediate string builder in implementation)

[julealgon]

@Lanayx please add a proper title to the issue so people are not forced to open the link to see what it is about.

[Lanayx]

Thank you for noticing, done

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