fix(git): add vendor in .gitignore

vendor/github.com/json-iterator/go/Gopkg.toml

@@ -1,26 +0,0 @@
-# Gopkg.toml example
-#
-# Refer to https://github.com/golang/dep/blob/master/docs/Gopkg.toml.md
-# for detailed Gopkg.toml documentation.
-#
-# required = ["github.com/user/thing/cmd/thing"]
-# ignored = ["github.com/user/project/pkgX", "bitbucket.org/user/project/pkgA/pkgY"]
-#
-# [[constraint]]
-#   name = "github.com/user/project"
-#   version = "1.0.0"
-#
-# [[constraint]]
-#   name = "github.com/user/project2"
-#   branch = "dev"
-#   source = "github.com/myfork/project2"
-#
-# [[override]]
-#  name = "github.com/x/y"
-#  version = "2.4.0"
-
-ignored = ["github.com/davecgh/go-spew*","github.com/google/gofuzz*","github.com/stretchr/testify*"]
-
-[[constraint]]
-  name = "github.com/modern-go/reflect2"
-  version = "1.0.1"