Fixes parse_hashtag() in damus.c so hashtags no longer include non-al…

…phanumeric characters such as punctuation marks.

Closes: damus-io#1518

damus-c/damus.c

@@ -72,7 +72,7 @@ static int parse_hashtag(struct cursor *cur, struct note_block *block) {
         return 0;
     }
 
-    consume_until_boundary(cur);
+    consume_until_non_alphanumeric(cur, 1);
 
     block->type = BLOCK_HASHTAG;
     block->block.str.start = (const char*)(start + 1);