KeywordReplace.cs

using UnityEngine;
using UnityEditor;

public class KeywordReplace : UnityEditor.AssetModificationProcessor
{
    public static void OnWillCreateAsset(string path)
    {
        path = path.Replace(".meta", "");
        int index = path.LastIndexOf(".");
        string file;
        try
        {
            file = path.Substring(index);
        }
        catch (System.ArgumentOutOfRangeException)
        {
            return;
        }
        if (!file.Contains(".cs")) return;
        index = Application.dataPath.LastIndexOf("Assets");
        path = Application.dataPath.Substring(0, index) + path;
        file = System.IO.File.ReadAllText(path);
        string[] splitPath = path.Split('/');
        string folder = splitPath[splitPath.Length - 2];

        file = file.Replace("#NAMESPACE#", folder);
        file = file.Replace("#CREATIONDATE#", System.DateTime.Now + "");
        file = file.Replace("#PROJECTNAME#", PlayerSettings.productName);
        file = file.Replace("#DEVELOPERS#", PlayerSettings.companyName);

        System.IO.File.WriteAllText(path, file);
        AssetDatabase.Refresh();
    }
}