Add readonly getters and setters for input fields

src/elements.ts

@@ -612,13 +612,13 @@
 
     // hack to avoid TS notification
     // about setting undefined value to readonly properties
     delete (this as any)._el;
     delete (this as any)._data;
     delete (this as any)._events;
 
     // remove mutation observer instances
     delete (this as any)._mutationObserver;
     delete (this as any)._mutationObserverCallbacks;
   }
 
   /** Removes this element. */
@@ -1045,7 +1045,7 @@
     if (!obj) return this.setAttr('d', '');
     const attributes: SVGDrawingOptions = {};
     for (const p of ['mark', 'arrows', 'round'] as const) {
       if (this.hasAttr(p)) attributes[p] = this.attr(p) as any;
     }
     if (this.hasClass('fill')) attributes.fill = 'fill';
     if (this.hasAttr('size')) attributes.size = (+this.attr('size')) || undefined;
@@ -1248,6 +1248,14 @@
     (this._el as HTMLInputElement).checked = value;
   }
 
+  get readonly() {
+    return (this._el as HTMLInputElement).readOnly;
+  }
+
+  set readonly(value: boolean) {
+    (this._el as HTMLInputElement).readOnly = value;
+  }
+
   get value() {
     return this._el.value;
   }