Add URL encoding support and index.html automatic mapping support in ContentRouteHandler

[ChZhongPengCheng33]

Add the following code after here:

if (filePath.EndsWith("/"))
{
    filePath += "index.html";
}
filePath = WebUtility.UrlDecode(filePath);

After adding the above code, my Vitespress documentation website can now function properly.

[jchristn]

Resolved in v6.1.5, thanks @ChZhongPengCheng33