fix(linkList): add aria attribute to item-card (#5010)

### Related Ticket(s)

#4060 

### Description

To provide each link-list-item-card with a landmark region and appropriate label to convey beginning and ending boundary for the screen reader user. 

### Changelog

**New**

- `aria-label` attribute

**Changed**

- `role` to using `region`

<!-- React and Web Component deploy previews are enabled by default. -->
<!-- To enable additional available deploy previews, apply the following -->
<!-- labels for the corresponding package: -->
<!-- *** "package: services": Services -->
<!-- *** "package: utilities": Utilities -->
<!-- *** "package: styles": Carbon Expressive -->
<!-- *** "RTL": React / Web Components (RTL) -->
<!-- *** "feature flag": React / Web Components (experimental) -->

packages/web-components/src/components/link-list/link-list-item-card.ts

@@ -1,7 +1,7 @@
 /**
  * @license
  *
- * Copyright IBM Corp. 2020
+ * Copyright IBM Corp. 2020, 2021
  *
  * This source code is licensed under the Apache-2.0 license found in the
  * LICENSE file in the root directory of this source tree.
@@ -23,7 +23,10 @@ const { stablePrefix: ddsPrefix } = ddsSettings;
 class DDSLinkListItem extends DDSCardLink {
   connectedCallback() {
     if (!this.hasAttribute('role')) {
-      this.setAttribute('role', 'listitem');
+      this.setAttribute('role', 'region');
+    }
+    if (this.innerText) {
+      this.setAttribute('aria-label', this.innerText);
     }
     super.connectedCallback();
   }