nostrdb/Inital embedded content parser

This adds some initial code for nostrdb content parsing.

We still need to write tests for encoding and decoding, so this is
likely not working yet.

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

nostrdb/src/nostrdb.c

@@ -57,7 +57,6 @@ typedef int (*ndb_word_parser_fn)(void *, const char *word, int word_len,
 // representation
 #pragma pack(push, 1)
 
-
 union ndb_packed_str {
 	struct {
 		char str[3];
@@ -99,6 +98,7 @@ struct ndb_note {
 
 #pragma pack(pop)
 
+
 struct ndb_migration {
 	ndb_migrate_fn fn;
 };