addition: Base for implementation

include/graph.h

@@ -1,6 +1,20 @@
 #ifndef GRAPH_H
 #define GRAPH_H
 
+#include <stdlib.h>
+
+typedef struct Graph Graph;
+typedef struct Vertex Vertex;
+typedef struct Edge Edge;
+
+typedef enum {
+    GRAPH_OK,
+} GraphErr ;
+
+typedef enum {
+    GRAPH_DIRECTED,
+    GRAPH_UNDIRECTED,
+} GraphType;
 
 
 #endif