move Newtsonsoft concerns to a new package `SonghayCore.Newtonsoft`

[BryanWilhite]

even though this is annoying and tedious adding this new package, SonghayCore.Newtonsoft, is a time-saving compromise compared to weeding out all of my Newtonsoft investments in one go

ideally this netstandard2.0 package will not depend on SonghayCore and should freeze in time or be locked in the Newtonsoft time frame

• [x] replace Newtonsoft attributes on OPML models with Microsoft equivalents
• [x] add new projects, SonghayCore.Newtonsoft and SonghayCore.Newtonsoft.Tests
• [x] move Newtonsoft concerns to new projects
• [x] publish SonghayCore.Newtonsoft NuGet netstandard2.0 package

[BryanWilhite]

according to https://github.com/dotnet/runtime/issues/30180#issuecomment-557782346, [DataContract(Name = "opml")] is the equivalent of [JsonObject("opml")]

<| @layomia

[BryanWilhite]

ITemporalExtensions.ToJObject will be removed from the Core:

/// <summary>
/// Converts the specified <see cref="ITemporal"/> data
/// to <see cref="JObject"/>.
/// </summary>
/// <param name="data">the <see cref="ITemporal"/> data</param>
/// <param name="useJavaScriptCase">when <c>true</c> use snakecase</param>
/// <typeparam name="TData">a type derived from <see cref="ITemporal"/></typeparam>
public static JObject ToJObject<TData>(this ITemporal data, bool useJavaScriptCase) where TData : class, ITemporal
{
    if (data == null) return null;

    var settings = JsonSerializationUtility
        .GetConventionalResolver<TData>(useJavaScriptCase)
        .ToJsonSerializerSettings()
        .WithConventionalSettings()
        ;

    var jO = JObject.FromObject(data, JsonSerializer.Create(settings));

    return jO;
}

[BryanWilhite]

new repo: https://github.com/BryanWilhite/SonghayCore.Newtonsoft :octocat: ✨