Publish OpenApiDiff to Nuget (or make dotnet cli tool)

Having this tool as a node package is great... but having it as a nuget package or dotnet CLI tool would be even better for those of us who have API's without javascript frontends. Otherwise I need to add node to my build pipeline in order to use it.

首先檢查現有的 Node 套件和 OpenApiDiff 的命令列進入點。確定如何在不需要 Node 的情況下建置和發佈 NuGet 套件或 .NET CLI 工具；當使用者可以從以 .NET 為基礎的建置管線安裝並執行它，且已發佈的成品有文件說明時，即視為完成。

由索引模型根據 Issue 內容生成。