Add header to header_config

headers/header_config.txt

+##########################################################################
+#                                                                        #
+#  This file is part of the Frama-C's MetACSL plug-in.                   #
+#                                                                        #
+#  Copyright (C) 2018-2022                                               #
+#    CEA (Commissariat à l'énergie atomique et aux énergies              #
+#         alternatives)                                                  #
+#                                                                        #
+#  you can redistribute it and/or modify it under the terms of the GNU   #
+#  Lesser General Public License as published by the Free Software       #
+#  Foundation, version 2.1.                                              #
+#                                                                        #
+#  It is distributed in the hope that it will be useful,                 #
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of        #
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         #
+#  GNU Lesser General Public License for more details.                   #
+#                                                                        #
+#  See the GNU Lesser General Public License version 2.1                 #
+#  for more details (enclosed in the file LICENSE)                       #
+#                                                                        #
+##########################################################################
+
+#################
+# Header config #
+#################
+
+| "header_config.txt" -> frame open:"#"  line:"#" close:"#"
+
+#############
+# CONFIGURE #
+#############
+
 | ".*configure\..*" -> frame open:"#"  line:"#" close:"#"
 
 ##########