adds an unauthenticated Bluesky archiver (#160)

* adds a TODO for next code iterations

* implements bsky archiver

* adds new archiver to example orchestration file

* Fix downloading media for posts with multiple images

(Images are stored in media/images)

* Setup a basic framework for unit tests

Use 'python -m unittest' from the project root to run

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Co-authored-by: Patrick Robertson <robertson.patrick@gmail.com>

example.orchestration.yaml

@@ -2,6 +2,7 @@ steps:
   # only 1 feeder allowed
   feeder: gsheet_feeder # defaults to cli_feeder
   archivers: # order matters, uncomment to activate
+    - bluesky_archiver
     # - vk_archiver
     # - telethon_archiver
     # - telegram_archiver