fix(git): add vendor in .gitignore

vendor/github.com/json-iterator/go/jsoniter.go

@@ -1,18 +0,0 @@
-// Package jsoniter implements encoding and decoding of JSON as defined in
-// RFC 4627 and provides interfaces with identical syntax of standard lib encoding/json.
-// Converting from encoding/json to jsoniter is no more than replacing the package with jsoniter
-// and variable type declarations (if any).
-// jsoniter interfaces gives 100% compatibility with code using standard lib.
-//
-// "JSON and Go"
-// (https://golang.org/doc/articles/json_and_go.html)
-// gives a description of how Marshal/Unmarshal operate
-// between arbitrary or predefined json objects and bytes,
-// and it applies to jsoniter.Marshal/Unmarshal as well.
-//
-// Besides, jsoniter.Iterator provides a different set of interfaces
-// iterating given bytes/string/reader
-// and yielding parsed elements one by one.
-// This set of interfaces reads input as required and gives
-// better performance.
-package jsoniter