Added QR code scanner as tunnel import method

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

app/src/main/java/com/wireguard/config/Config.java

@@ -20,6 +20,7 @@ import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
+import java.io.StringReader;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.List;
@@ -32,6 +33,10 @@ public class Config {
     private final Interface interfaceSection = new Interface();
     private List<Peer> peers = new ArrayList<>();
 
+    public static Config from(final String string) throws IOException {
+        return from(new BufferedReader(new StringReader(string)));
+    }
+
     public static Config from(final InputStream stream) throws IOException {
         return from(new BufferedReader(new InputStreamReader(stream, StandardCharsets.UTF_8)));
     }