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.

crates/bindings/npm/package.json.in

@@ -1,5 +1,5 @@
 {
-  "name": "catena",
+  "name": "catena-corpus",
   "version": "@VERSION@",
   "description": "Turn a pile of files into a searchable corpus: chunking, scrubbing, subtitles and rank fusion, as WebAssembly",
   "license": "MPL-2.0",