Make placeholder pretty

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

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

@@ -7,4 +7,7 @@
     <color name="fab_label_background_color">#444444</color>
 
     <color name="accent">#2196F3</color>
+
+    <!-- TODO(msf): replace with ?android:attr/colorBackground with some alpha -->
+    <color name="transparent_background_placeholder">#aafafafa</color>
 </resources>

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

@@ -89,6 +89,7 @@
     <string name="tools_installer_title">Install command line tools</string>
     <string name="tunnel_create_error">Unable to create tunnel: %s</string>
     <string name="tunnel_create_success">Successfully created tunnel “%s”</string>
+    <string name="tunnel_list_placeholder">Add a tunnel using the blue button</string>
     <string name="tunnel_rename_error">Unable to rename tunnel: %s</string>
     <string name="tunnel_rename_success">Successfully renamed tunnel to “%s”</string>
     <string name="version_title">WireGuard for Android v%s"</string>
@@ -99,5 +100,4 @@
     <string name="zip_export_error">Unable to export tunnels: %s</string>
     <string name="zip_export_success">Saved to %s</string>
     <string name="zip_export_summary">Zip file will be saved to downloads folder</string>
-    <string name="no_tunnels_imported_placeholder">Tap the button at the bottom to begin</string>
 </resources>