feat(combobox): adding shadow parts

packages/carbon-web-components/src/components/combo-box/combo-box.ts

@@ -26,6 +26,8 @@ export { DROPDOWN_DIRECTION, DROPDOWN_SIZE } from '../dropdown/dropdown';
  * Combo box.
  *
  * @element cds-combo-box
+ * @csspart text-input - The text input. Usage `cds-combo-box::part(text-input)`
+ * @csspart list-box - The list box. Usage `cds-combo-box::part(list-box)`
  * @fires cds-combo-box-beingselected
  *   The custom event fired before a combo box item is selected upon a user gesture.
  *   Cancellation of this event stops changing the user-initiated selection.
@@ -239,6 +241,7 @@ class CDSComboBox extends CDSDropdown {
 
     return html`
       <input
+        part="text-input"
         id="trigger-button"
         class="${inputClasses}"
         ?disabled=${disabled}
@@ -271,6 +274,7 @@ class CDSComboBox extends CDSDropdown {
       ? undefined
       : html`
           <div
+            part="list-box"
             id="selection-button"
             role="button"
             class="${prefix}--list-box__selection"