[twitter] set 'retweet_id' for original retweets (#1481)

gallery_dl/extractor/twitter.py

@@ -485,6 +485,7 @@ class TwitterTweetExtractor(TwitterExtractor):
             "count": 2,
             "keyword": {
                 "tweet_id"  : 1296296016002547713,
+                "retweet_id": 1296296016002547713,
                 "date"      : "dt:2020-08-20 04:00:28",
             },
         }),
@@ -806,6 +807,7 @@ class TwitterAPI():
                     if original_retweets:
                         if not retweet:
                             continue
+                        retweet["retweeted_status_id_str"] = retweet["id_str"]
                         retweet["_retweet_id_str"] = tweet["id_str"]
                         tweet = retweet
                     elif retweet: