[unity] Added a warning when a `.skel` file is found instead of `.skel.bytes` during import.

spine-unity/Assets/Spine/Editor/spine-unity/Editor/Utility/AssetUtility.cs

@@ -338,6 +338,11 @@ namespace Spine.Unity.Editor {
 						Debug.LogWarningFormat("`{0}` : If this file is a Spine atlas, please change its extension to `.atlas.txt`. This is to allow Unity to recognize it and avoid filename collisions. You can also set this file extension when exporting from the Spine editor.", str);
 					}
 					break;
+				case ".skel":
+					if (SpineEditorUtilities.Preferences.atlasTxtImportWarning) {
+						Debug.LogWarningFormat("`{0}` : If this file is a Spine skeleton, please change its extension to `.skel.bytes`. This is to allow Unity to recognize it and avoid filename collisions. You can also set this file extension when exporting from the Spine editor.", str);
+					}
+					break;
 				case ".txt":
 					if (str.EndsWith(".atlas.txt", System.StringComparison.Ordinal))
 						atlasPaths.Add(str);

spine-unity/Assets/Spine/Editor/spine-unity/Editor/Windows/SpinePreferences.cs

@@ -288,7 +288,7 @@ namespace Spine.Unity.Editor {
 				EditorGUILayout.Space();
 				EditorGUILayout.LabelField("Warnings", EditorStyles.boldLabel);
 				{
-					EditorGUILayout.PropertyField(settings.FindProperty("atlasTxtImportWarning"), new GUIContent("Atlas Extension Warning", "Log a warning and recommendation whenever a `.atlas` file is found."));
+					EditorGUILayout.PropertyField(settings.FindProperty("atlasTxtImportWarning"), new GUIContent("Atlas & Skel Extension Warning", "Log a warning and recommendation whenever a `.atlas` or `.skel` file is found."));
 					EditorGUILayout.PropertyField(settings.FindProperty("textureImporterWarning"), new GUIContent("Texture Settings Warning", "Log a warning and recommendation whenever Texture Import Settings are detected that could lead to undesired effects, e.g. white border artifacts."));
 					EditorGUILayout.PropertyField(settings.FindProperty("componentMaterialWarning"), new GUIContent("Component & Material Warning", "Log a warning and recommendation whenever Component and Material settings are not compatible."));
 				}