Allow ListItem components to link to external links

Closes #3039

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

src/components/ListItem/ListItem.vue

@@ -171,10 +171,14 @@
 	<listItem
 		:title="'Title of the element'"
 		:counter-number=4
+		href="https://nextcloud.com"
 		:compact="true" >
 		<template #icon>
 			<div class="icon-edit" />
 		</template>
+		<template #subtitle>
+			This one is with an external link
+		</template>
 	</listItem>
 </ul>
 ```
@@ -187,7 +191,9 @@
 		<a :id="anchorId"
 			ref="list-item"
 			:class="{ 'list-item--active' : active }"
-			href="#"
+			:href="href"
+			target="_blank"
+			rel="noopener noreferrer"
 			class="list-item"
 			:aria-label="linkAriaLabel"
 			@mouseover="handleMouseover"
@@ -319,6 +325,14 @@ export default {
 			default: '',
 		},
 
+		/**
+		 * The value for the external link
+		 */
+		href: {
+			type: String,
+			default: '#',
+		},
+
 		/**
 		 * Id for the <a> element
 		 */