Add local npm registry publish and install

README.md

@@ -279,6 +279,20 @@ content-addressable store (deduplicated by digest, reaped by GC once
 unreferenced); tags are mutable references and re-pushing a tag moves it. Blob
 uploads support both the monolithic and chunked (`POST`/`PATCH`/`PUT`) flows.
 
+### Local npm registry
+
+A local `npm` repo is a real npm registry: `npm publish` (scoped and unscoped)
+and `npm install` work against `/api/v1/local/{name}/`. npm requires an
+`_authToken` for the registry before it will publish; any value works.
+
+```ini
+# .npmrc
+registry=https://artifactapi.k8s.syd1.au.unkin.net/api/v1/local/npm-internal/
+//artifactapi.k8s.syd1.au.unkin.net/api/v1/local/npm-internal/:_authToken=unused
+```
+
+Versions are immutable; dist-tags sent with a publish move to that version.
+
 ## Access Control
 
 | Field | Default | Behaviour |
@@ -297,6 +311,7 @@ No patterns + no blocklist = open proxy. Provider handles mutability classificat
 ```
 GET /api/v1/remote/{name}/{path}     Proxy/cache artifact
 GET /api/v1/virtual/{name}/{path}    Virtual repo (merged index)
+PUT /api/v1/local/{name}/{package}   npm publish (local npm repos)
 GET /v2/{name}/{path}                Docker Registry v2
 ```