docs: add title for socket providers section

src.ts/providers/provider-socket.ts

@@ -6,7 +6,7 @@
  *  - a sub-class MUST override the `_write(string)` method
  *  - a sub-class MUST call `_processMessage(string)` for each message
  *
- *  @_subsection: api/providers/abstract-provider
+ *  @_subsection: api/providers/abstract-provider:Socket Providers  [about-socketProvider]
  */
 
 import { UnmanagedSubscriber } from "./abstract-provider.js";