[twitter] add 'birdwatch' metadata field (#5317)

should probably get a better name,
but this is what it's called internally by Twitter

gallery_dl/extractor/twitter.py

@@ -340,6 +340,8 @@ class TwitterExtractor(Extractor):
         txt, _, tco = content.rpartition(" ")
         tdata["content"] = txt if tco.startswith("https://t.co/") else content
 
+        if "birdwatch_pivot" in tweet:
+            tdata["birdwatch"] = tweet["birdwatch_pivot"]["subtitle"]["text"]
         if "in_reply_to_screen_name" in legacy:
             tdata["reply_to"] = legacy["in_reply_to_screen_name"]
         if "quoted_by" in legacy:

test/results/twitter.py

@@ -590,6 +590,17 @@ The Washington Post writes, "Three weeks after the toxic train derailment in Ohi
 "The analysis by Texas A&M University seems to contradict statements by state and federal regulators that air near the crash site is completely safe, despite residents complaining about rashes, breathing problems and other health effects." Your reaction.""",
 },
 
+{
+    "#url"     : "https://twitter.com/KrisKobach1787/status/1765935595702919299",
+    "#comment" : "'birdwatch' note (#5317)",
+    "#category": ("", "twitter", "tweet"),
+    "#class"   : twitter.TwitterTweetExtractor,
+    "#options"  : {"text-tweets": True},
+
+    "birdwatch": "In addition to the known harm of lead exposure, especially to children, Mr. Kobach is incorrect when he states the mandate is unfunded. In fact, the BIPARTISAN Infrastructure Law Joe Biden signed into law in Nov 2021 provides $15B toward lead service line replacement projects. epa.gov/ground-water-a…",
+    "content"  : "Biden wants to replace lead pipes. He failed to mention that the unfunded mandate sets an almost impossible timeline, will cost billions, infringe on the rights of the States and their residents – all for benefits that may be entirely speculative. #sotu https://ag.ks.gov/media-center/news-releases/2024/02/09/kobach-leads-coalition-demanding-biden-drop-unnecessary-epa-rule",
+},
+
 {
     "#url"     : "https://twitter.com/playpokemon/status/1263832915173048321/quotes",
     "#category": ("", "twitter", "quotes"),