fix some accessiblity warnings

app/src/main/res/layout/channel_fragment.xml

@@ -88,7 +88,7 @@
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginEnd="96dp"
-        android:contentDescription="@string/share_button"
+        android:contentDescription="@string/share"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintTop_toTopOf="@+id/editableCheckbox"
         app:srcCompat="@drawable/ic_twotone_share_24" />

app/src/main/res/layout/messages_fragment.xml

@@ -12,6 +12,7 @@
         android:layout_marginTop="8dp"
         android:layout_marginEnd="8dp"
         android:layout_marginBottom="8dp"
+        android:contentDescription="Text messages"
         app:layout_constraintBottom_toTopOf="@+id/textInputLayout"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"

app/src/main/res/layout/nodelist_fragment.xml

@@ -2,7 +2,8 @@
 <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
-    android:layout_height="match_parent">
+    android:layout_height="match_parent"
+    android:contentDescription="A list of nodes in the mesh">
 
     <androidx.recyclerview.widget.RecyclerView
         android:id="@+id/nodeListView"

app/src/main/res/values/strings.xml

@@ -49,4 +49,5 @@
     <string name="pairing_completed">Pairing completed, starting service</string>
     <string name="pairing_failed_try_again">Pairing failed, please select again</string>
     <string name="location_disabled">Location access is disabled, can not provide position to the mesh.</string>
+    <string name="share">Share</string>
 </resources>