Allow the user to add a "bookmarks" tab (#3983)

Fixes #2368

app/src/main/java/com/keylesspalace/tusky/TabData.kt

@@ -36,6 +36,7 @@ const val DIRECT = "Direct"
 const val TRENDING_TAGS = "TrendingTags"
 const val HASHTAG = "Hashtag"
 const val LIST = "List"
+const val BOOKMARKS = "Bookmarks"
 
 data class TabData(
     val id: String,
@@ -114,6 +115,12 @@ fun createTabDataFromId(id: String, arguments: List<String> = emptyList()): TabD
             arguments = arguments,
             title = { arguments.getOrNull(1).orEmpty() }
         )
+        BOOKMARKS -> TabData(
+            id = BOOKMARKS,
+            text = R.string.title_bookmarks,
+            icon = R.drawable.ic_bookmark_active_24dp,
+            fragment = { TimelineFragment.newInstance(TimelineViewModel.Kind.BOOKMARKS) }
+        )
         else -> throw IllegalArgumentException("unknown tab type")
     }
 }

app/src/main/java/com/keylesspalace/tusky/TabPreferenceActivity.kt

@@ -382,6 +382,10 @@ class TabPreferenceActivity : BaseActivity(), Injectable, ItemInteractionListene
         if (!currentTabs.contains(trendingTagsTab)) {
             addableTabs.add(trendingTagsTab)
         }
+        val bookmarksTab = createTabDataFromId(BOOKMARKS)
+        if (!currentTabs.contains(trendingTagsTab)) {
+            addableTabs.add(bookmarksTab)
+        }
 
         addableTabs.add(createTabDataFromId(HASHTAG))
         addableTabs.add(createTabDataFromId(LIST))