nostrdb/content_parser: add initial db decoders

We need to pull the data out as well! Let's add some initial decoders.
We still need tests to make sure it's working.

Signed-off-by: William Casarin <jb55@jb55.com>

nostrdb/src/nostrdb.h

@@ -198,6 +198,12 @@ struct ndb_builder {
 	struct ndb_tag *current_tag;
 };
 
+/*
+struct ndb_block_iterator {
+	struct note_block block;
+};
+*/
+
 struct ndb_iterator {
 	struct ndb_note *note;
 	struct ndb_tag *tag;
@@ -390,4 +396,6 @@ int ndb_parse_content(unsigned char *buf, int buf_size,
 		      const char *content, int content_len,
 		      struct ndb_note_blocks **blocks_p);
 
+//int ndb_blocks_iterate_next(struct ndb_block_iterator *iter);
+
 #endif