unity editor下，代码添加指定场景到BuildSetting，并把这个场景作为初始场景

在Unity Editor下，可以通过以下代码实现将指定场景添加到Build Settings并将其作为初始场景：

using UnityEditor;
using UnityEngine.SceneManagement;

public class BuildSettingsManager
{
    [MenuItem("MyMenu/Add Scene To Build Settings")]
    static void AddSceneToBuildSettings()
    {
        // Get the path of the scene to add
        string scenePath = "Assets/Scenes/MyScene.unity";

        // Get the current Build Settings
        EditorBuildSettingsScene[] buildScenes = EditorBuildSettings.scenes;

        // Check if the scene is already in the Build Settings
        bool isAlreadyAdded = false;
        foreach (EditorBuildSettingsScene buildScene in buildScenes)
        {
            if (buildScene.path == scenePath)
            {
                isAlreadyAdded = true;
                break;
            }
        }

        // If the scene is not in the Build Settings, add it
        if (!isAlreadyAdded)
        {
            EditorBuildSettingsScene[] newBuildScenes = new EditorBuildSettingsScene[buildScenes.Length + 1];

            for (int i = 0; i < buildScenes.Length; i++)
            {
                newBuildScenes[i] = buildScenes[i];
            }

            newBuildScenes[newBuildScenes.Length - 1] = new EditorBuildSettingsScene(scenePath, true);
            EditorBuildSettings.scenes = newBuildScenes;
        }

        // Set the added scene as the first scene in the Build Settings
        for (int i = 0; i < buildScenes.Length; i++)
        {
            if (buildScenes[i].path == scenePath)
            {
                EditorBuildSettings.scenes[i].enabled = true;
                EditorBuildSettings.scenes[i].moveToTop = true;
                break;
            }
        }

        // Set the added scene as the initial scene
        Scene scene = SceneManager.GetSceneByPath(scenePath);
        if (scene != null)
        {
            EditorSceneManager.playModeStartScene = scene;
        }
    }
}

这个脚本添加了一个菜单项"MyMenu/Add Scene To Build Settings"，可以通过点击这个菜单项来执行将指定场景添加到Build Settings并将其作为初始场景的操作。