[a11y] Add content descriptions to room list item indicators (#5236)

* [a11y] Add content descriptions to room list item indicators. These can now be read aloud as 'ongoing call', 'new messages', 'new mentions'.

* Add `contentDescription` to `UnreadIndicatorAtom` as an optional value

* Make the 'ongoing call', 'new messages', etc. indicators be read aloud before the latest event of the room summary

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Co-authored-by: ElementBot <android@element.io>

libraries/designsystem/src/main/kotlin/io/element/android/libraries/designsystem/atomic/atoms/UnreadIndicatorAtom.kt

@@ -15,6 +15,8 @@ import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.semantics.contentDescription
+import androidx.compose.ui.semantics.semantics
 import androidx.compose.ui.unit.Dp
 import androidx.compose.ui.unit.dp
 import io.element.android.compound.theme.ElementTheme
@@ -28,9 +30,13 @@ fun UnreadIndicatorAtom(
     size: Dp = 12.dp,
     color: Color = ElementTheme.colors.unreadIndicator,
     isVisible: Boolean = true,
+    contentDescription: String? = null,
 ) {
     Box(
         modifier = modifier
+            .semantics {
+                contentDescription?.let { this.contentDescription = it }
+            }
             .size(size)
             .clip(CircleShape)
             .background(if (isVisible) color else Color.Transparent)