publish as catena-corpus on PyPI and npm

Both registries already have a `catena`: an HPE blockchain client on PyPI,
and a JavaScript OOP wrapper at 2.2.0 on npm. Neither is going anywhere, so
the distributions take a name that is free on both.

The Python import is unaffected — a distribution name and a module name are
independent there, so `pip install catena-corpus` still gives `import
catena`, and nothing in the examples or the bindings changes. On npm the
package name is the import specifier, so that one does change: `import
{ chunkMarkdown } from "catena-corpus"`.

The crates keep their own names. `catena` is free on crates.io.

examples/README.md

@@ -75,12 +75,12 @@ convert, then loop, and what is left is the part that is actually about your
 schema.
 
 ```sh
-pip install catena
+pip install catena-corpus
 python examples/python/book_to_citations.py
 ```
 
 ```sh
-pip install catena psycopg
+pip install catena-corpus psycopg
 DATABASE_URL=postgresql://user@host/db \
     python examples/python/search_and_rerank.py "why did the empire decline"
 ```