Add 'Gift access' — documenting the member gift-account feature

getting-started.md

@@ -43,6 +43,8 @@ or contact anyone.
 - **API access** for your own tools and projects (see [API access](api-access.md)).
 - **A monthly usage allowance** of $15 of credit, shared between chat and API.
 - **Credit packs** — buy extra non-expiring credits when you need more.
+- **Gift access** — give a friend $5 of credit and 60 days of the co-op.
+  See [Gift access](gift-access.md).
 - **A voice in governance** — how the project is run and where it goes next.
 
 ## 2. Use the chat