feat(setup): set long_description to readme

Signed-off-by: John Andersen <[email protected]>

pyproject.toml

@@ -3,6 +3,7 @@ name = "gitatp"
 version = "0.1.0"
 description = "Git over ATproto"
 long_description_content_type = "text/markdown"
+long_description = file: README.md
 readme = "README.md"
 authors = [
     { name = "John Andersen", email = "[email protected]" }