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>

tests/__init__.py

@@ -0,0 +1,4 @@
+import unittest
+
+if __name__ == '__main__':
+    unittest.main()