Add .ohwr.yaml

.ohwr.yaml

+---
+# SPDX-FileCopyrightText: 2024 CERN (home.cern)
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+version: '1.0.0'
+name: 'CITY - CarrIer for RFoWR-based Timing sYstems'
+description: 'https://ohwr.org/project/city/wikis/home'
+website: 'https://ohwr.org/project/city'
+documentation: 'https://ohwr.org/project/city/wikis'
+issues: 'https://ohwr.org/project/city/issues'
+