fix(sbb-icon): ensure sbb-angular compatibility (#3081)

src/elements/icon/icon.ts

@@ -8,6 +8,15 @@ import { SbbIconBase } from './icon-base.js';
  */
 @customElement('sbb-icon')
 export class SbbIconElement extends SbbIconBase {
+  /**
+   * We need to additionally observe the svgicon attribute
+   * for sbb-angular compatibility.
+   * @internal
+   */
+  public static override get observedAttributes(): string[] {
+    return super.observedAttributes.concat('svgicon');
+  }
+
   /**
    * The provided name consisting of the namespace and the name of the icon.
    * If the namespace is missing, the default namespace "sbb" will be used.