re-implement default slot for additional ui

Author: nielslyngsoe

packages/uui-file-dropzone/lib/uui-file-dropzone.element.ts

@@ -4,6 +4,7 @@ import { query, property } from 'lit/decorators.js';
 import { UUIFileDropzoneEvent } from './UUIFileDropzoneEvents';
 import { LabelMixin } from '@umbraco-ui/uui-base/lib/mixins';
 import { demandCustomElement } from '@umbraco-ui/uui-base/lib/utils';
+import '@umbraco-ui/uui-button/lib/';
 
 /**
  * @element uui-file-dropzone
@@ -257,6 +258,7 @@ export class UUIFileDropzoneElement extends LabelMixin('', LitElement) {
           ?multiple=${this.multiple}
           @change=${this._onFileInputChange}
           aria-label="${this.label}" />
+        <slot></slot>
       </div>
     `;
   }