add vendoring

vendor/github.com/rs/zerolog/internal/json/base.go

@@ -0,0 +1,19 @@
+package json
+
+// JSONMarshalFunc is used to marshal interface to JSON encoded byte slice.
+// Making it package level instead of embedded in Encoder brings
+// some extra efforts at importing, but avoids value copy when the functions
+// of Encoder being invoked.
+// DO REMEMBER to set this variable at importing, or
+// you might get a nil pointer dereference panic at runtime.
+var JSONMarshalFunc func(v interface{}) ([]byte, error)
+
+type Encoder struct{}
+
+// AppendKey appends a new key to the output JSON.
+func (e Encoder) AppendKey(dst []byte, key string) []byte {
+	if dst[len(dst)-1] != '{' {
+		dst = append(dst, ',')
+	}
+	return append(e.AppendString(dst, key), ':')
+}