Better accessibility support

Add ContentDescription to items when no label show.
When is set
```
.setTitleState(AHBottomNavigation.TitleState.ALWAYS_HIDE);
```
TalkBack has no text to read.

Simplest solution is when inflating items set
```
view.setContentDescription(item.getTitle(context));
```

Locate where AHBottomNavigation items are inflated and where TitleState.ALWAYS_HIDE affects their labels. Check how each item view is created, then verify that TalkBack can read the item title through its content description when no visible label is shown.

Written by the indexing model from the issue text.