nip19: add kind to naddr & nevent

Add support for type KIND for bech32-encoded entities naddr and nevent
as specified in NIP-19.

LNURL1DP68GURN8GHJ7EM9W3SKCCNE9E3K7MF0D3H82UNVWQHKWUN9V4HXGCTHDC6RZVGR8SW3G

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

damus-c/nostr_bech32.h

@@ -11,6 +11,8 @@
 #include <stdio.h>
 #include "str_block.h"
 #include "cursor.h"
+#include <stdbool.h>
+
 typedef unsigned char u8;
 #define MAX_RELAYS 10
 
@@ -45,6 +47,8 @@ struct bech32_nevent {
     struct relays relays;
     const u8 *event_id;
     const u8 *pubkey; // optional
+    uint32_t kind;
+    bool has_kind;
 };
 
 struct bech32_nprofile {
@@ -56,6 +60,7 @@ struct bech32_naddr {
     struct relays relays;
     struct str_block identifier;
     const u8 *pubkey;
+    uint32_t kind;
 };
 
 struct bech32_nrelay {