Add Mastodon toots loader (#5036)
# Add Mastodon toots loader.
Loader works either with public toots, or Mastodon app credentials. Toot
text and user info is loaded.
I've also added integration test for this new loader as it works with
public data, and a notebook with example output run now.
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Co-authored-by: Dev 2049 <dev.dev2049@gmail.com>
