Improve app update info

app/src/main/java/org/koitharu/kotatsu/main/ui/MainActivity.kt

@@ -295,7 +295,11 @@ class MainActivity :
 				navBar.getBadge(id)?.isVisible = false
 			} else {
 				val badge = navBar.getOrCreateBadge(id)
-				badge.number = counter
+				if (counter < 0) {
+					badge.clearNumber()
+				} else {
+					badge.number = counter
+				}
 				badge.isVisible = true
 			}
 		}

app/src/main/java/org/koitharu/kotatsu/settings/tools/ToolsFragment.kt

@@ -87,7 +87,8 @@ class ToolsFragment :
 			binding.cardUpdate.root.isVisible = false
 			return
 		}
-		binding.cardUpdate.textPrimary.text = getString(R.string.new_version_s, version.name)
+		binding.cardUpdate.textPrimary.text = getString(R.string.app_update_available_s, version.name)
+		binding.cardUpdate.textSecondary.text = version.description
 		binding.cardUpdate.root.isVisible = true
 	}