Add a node_api.h header file

apis/c/node/node_api.h

@@ -0,0 +1,11 @@
+#include <stddef.h>
+
+void *init_dora_context_from_env();
+void free_dora_context(void *dora_context);
+
+void *dora_next_input(void *dora_context);
+void read_dora_input_id(void *dora_input, char **out_ptr, size_t *out_len);
+void read_dora_input_data(void *dora_input, char **out_ptr, size_t *out_len);
+void free_dora_input(void *dora_input);
+
+int dora_send_output(void *dora_context, char *id_ptr, size_t id_len, char *data_ptr, size_t data_len);