fix(git): add vendor in .gitignore

vendor/github.com/spf13/viper/internal/encoding/json/codec.go

@@ -1,17 +0,0 @@
-package json
-
-import (
-	"encoding/json"
-)
-
-// Codec implements the encoding.Encoder and encoding.Decoder interfaces for JSON encoding.
-type Codec struct{}
-
-func (Codec) Encode(v interface{}) ([]byte, error) {
-	// TODO: expose prefix and indent in the Codec as setting?
-	return json.MarshalIndent(v, "", "  ")
-}
-
-func (Codec) Decode(b []byte, v interface{}) error {
-	return json.Unmarshal(b, v)
-}