Automatically save dirty scenes and assets as soon as you enter playmode.

SaveSceneOnPlay.cs

using UnityEngine;
using UnityEditor;
using UnityEditor.SceneManagement;

[InitializeOnLoad]
public class SaveSceneOnPlay
{
    static SaveSceneOnPlay()
    {
        EditorApplication.playmodeStateChanged += () =>
        {
            if (!EditorApplication.isPlaying && EditorApplication.isPlayingOrWillChangePlaymode)
            {
                Debug.Log("Autosaving dirty scenes and assets.");

                EditorSceneManager.SaveOpenScenes();
                AssetDatabase.SaveAssets();
            }
        };
    }
}