Allow loading initial data to yang-cli

Change-Id: I527d6998b518a65ffde827bcf2d56335f1fb210d
diff --git a/src/yang_access.hpp b/src/yang_access.hpp
index 7fa562c..acbcc08 100644
--- a/src/yang_access.hpp
+++ b/src/yang_access.hpp
@@ -39,6 +39,7 @@
 
     void addSchemaFile(const std::string& path);
     void addSchemaDir(const std::string& path);
+    void addDataFile(const std::string& path);
 
 private:
     std::vector<ListInstance> listInstances(const std::string& path) override;