Add YDocument.providers attribute

Author: davidbrochart

javascript/src/ydocument.ts

@@ -4,11 +4,22 @@
 |----------------------------------------------------------------------------*/
 
 import { JSONExt, JSONObject, JSONValue } from '@lumino/coreutils';
+import { IDisposable } from '@lumino/disposable';
 import { ISignal, Signal } from '@lumino/signaling';
 import { Awareness } from 'y-protocols/awareness';
 import * as Y from 'yjs';
 import type { DocumentChange, ISharedDocument, StateChange } from './api.js';
 
+/**
+ * An interface for a document provider.
+ */
+export interface IDocumentProvider extends IDisposable {
+  /**
+   * Returns a Promise that resolves when the document provider is ready.
+   */
+  readonly ready: Promise<void>;
+}
+
 /**
  * Generic shareable document.
  */
@@ -200,6 +211,7 @@ export abstract class YDocument<T extends DocumentChange>
   private _awareness: Awareness;
   private _isDisposed = false;
   private _disposed = new Signal<this, void>(this);
+  providers: IDocumentProvider[] = [];
 }
 
 /**