Twoot can now handle threads. All tweets can again be uploaded on Mastodon. Tweets in a threads are displayed in reverse chronological order in the main timeline (first tweet on top) to improve readability. A list of nitter instances to use can now be specified in the config file e.g. `nitter_instances = ["nitter.nl", "nitter.fdn.fr"]`. If none is specified, the built-in list of 2-3 known good instances is used as before.