feat(webui): display read date on book details view

Closes: #757

komga-webui/src/locales/en.json

@@ -225,6 +225,7 @@
     "pending_tasks": "No pending tasks | 1 pending task | {count} pending tasks",
     "publisher": "Publisher",
     "read": "Read",
+    "read_on": "Read on {date}",
     "readlists": "Read Lists",
     "required": "Required",
     "reset_filters": "Reset filters",

komga-webui/src/views/BrowseBook.vue

@@ -117,6 +117,11 @@
           >
             {{ $tc('common.pages_left', pagesLeft) }}
           </div>
+          <div v-else-if="isRead"
+               class="text-caption text-center mt-1"
+          >
+            {{ $t('common.read_on', {date: readProgressDate}) }}
+          </div>
         </v-col>
 
         <v-col cols="8">
@@ -516,6 +521,14 @@ export default Vue.extend({
     readProgressPercentage(): number {
       return getReadProgressPercentage(this.book)
     },
+    readProgressDate(): string | undefined {
+      if (this.book.readProgress)
+        return new Intl.DateTimeFormat(this.$i18n.locale, {
+          dateStyle: 'medium',
+          timeStyle: 'short',
+        } as Intl.DateTimeFormatOptions).format(new Date(this.book.readProgress.lastModified))
+      return undefined
+    },
     previousId(): string {
       return this.siblingPrevious?.id?.toString() || '0'
     },