add viper
diff --git a/third_party/spf13/viper/README.google b/third_party/spf13/viper/README.google
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index 0000000..7761bcc
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+++ b/third_party/spf13/viper/README.google
@@ -0,0 +1,4 @@
+Viper is a set of tools for every kind of configuration file processing
+ever invented.
+
+URL: https://github.com/spf13/viper.git