Settings: add version

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

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

@@ -74,5 +74,9 @@
     <string name="tunnel_create_success">Successfully created tunnel “%s”</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>
+    <string name="version_kernel_summary">Using kernel module implementation v%s</string>
+    <string name="version_kernel_unknown_summary">Using unknown kernel module implementation</string>
+    <string name="version_userspace_summary">Using Go userspace implementation v%s</string>
     <string name="zip_exporter_title">Export tunnels to zip file</string>
 </resources>

app/src/main/res/xml/preferences.xml

@@ -13,4 +13,5 @@
         android:summaryOn="@string/dark_theme_summary_on"
         android:summaryOff="@string/dark_theme_summary_off"
         android:title="@string/dark_theme_title" />
+    <com.wireguard.android.preference.VersionPreference />
 </PreferenceScreen>