what changed does not detect custom extension change

[LasneF]

custom extension are supported for the license
https://spec.openapis.org/oas/latest.html#fixed-fields-2

given 2 spec with same license except that custom extension are not the same

they are seen as 100 % similar in the test case

func TestCompareLicense_Identicalz(t *testing.T) {

	left := `name: buckaroo
url: https://pb33f.io
x-myXtend : 324`

	right := `name: buckaroo
url: https://pb33f.io
x-myXtend : 325`

	var lNode, rNode yaml.Node
	_ = yaml.Unmarshal([]byte(left), &lNode)
	_ = yaml.Unmarshal([]byte(right), &rNode)

	// create low level objects
	var lDoc lowbase.License
	var rDoc lowbase.License
	_ = low.BuildModel(lNode.Content[0], &lDoc)
	_ = low.BuildModel(rNode.Content[0], &rDoc)
	_ = lDoc.Build(context.Background(), nil, lNode.Content[0], nil)
	_ = rDoc.Build(context.Background(), nil, rNode.Content[0], nil)

	// compare.
	extChanges := CompareLicense(&lDoc, &rDoc)
	assert.Nil(t, extChanges)
}