fab: add fab sized padding at bottom of recycler view

This way we can keep scrolling when there are exactly the right number
of items, so that the toggle switch becomes visible.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

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

@@ -30,6 +30,8 @@
             android:id="@+id/tunnel_list"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
+            android:paddingBottom="@dimen/design_fab_size_normal"
+            android:clipToPadding="false"
             android:choiceMode="multipleChoiceModal"
             app:items="@{tunnels}"
             app:layout="@{@layout/tunnel_list_item}"