[KBSWITCH][SDK] Add indicml.h and change window class (#7970)

Supporting the IME System Pen icon.
JIRA issue: CORE-19268
- Change kbswitch window class to "Indicator"
  from "kbswitcher".
- Add <ime/indicml.h> from DDK.

sdk/include/ime/indicml.h

@@ -0,0 +1,30 @@
+/*
+ * PROJECT:     ReactOS headers
+ * LICENSE:     LGPL-2.0-or-later (https://spdx.org/licenses/LGPL-2.0-or-later)
+ * PURPOSE:     Indicator (internat.exe) window class
+ * COPYRIGHT:   Copyright 2025 Katayama Hirofumi MZ (katayama.hirofumi.mz@gmail.com)
+ */
+
+#ifndef _INDICML_
+#define _INDICML_
+
+#pragma once
+
+#define INDICATOR_CLASSW L"Indicator"
+#define INDICATOR_CLASSA  "Indicator"
+
+#ifdef UNICODE
+#define INDICATOR_CLASS INDICATOR_CLASSW
+#else
+#define INDICATOR_CLASS INDICATOR_CLASSA
+#endif
+
+#define INDICM_SETIMEICON              (WM_USER + 100)
+#define INDICM_SETIMETOOLTIPS          (WM_USER + 101)
+#define INDICM_REMOVEDEFAULTMENUITEMS  (WM_USER + 102)
+
+/* wParam flags for INDICM_REMOVEDEFAULTMENUITEMS */
+#define RDMI_LEFT  1
+#define RDMI_RIGHT 2
+
+#endif /* ndef _INDICML_ */