Expose execution_state in the JS package

Author: krassowski

javascript/src/ycell.ts

@@ -749,6 +749,20 @@ export class YCodeCell
     }
   }
 
+  /**
+   * The code cell's execution state.
+   */
+  get execution_state(): 'running' | 'idle' {
+    return this.ymodel.get('execution_state') ?? 'idle';
+  }
+  set execution_state(state: 'running' | 'idle') {
+    if (this.ymodel.get('execution_state') !== state) {
+      this.transact(() => {
+        this.ymodel.set('execution_state', state);
+      }, false);
+    }
+  }
+
   /**
    * Cell outputs.
    */