Update dependencies for 1.18.0 release (#1175)

vendor/github.com/slack-go/slack/block_object.go

@@ -163,6 +163,7 @@ type ConfirmationBlockObject struct {
 	Text    *TextBlockObject `json:"text"`
 	Confirm *TextBlockObject `json:"confirm"`
 	Deny    *TextBlockObject `json:"deny"`
+	Style   Style            `json:"style,omitempty"`
 }
 
 // validateType enforces block objects for element and block parameters
@@ -170,6 +171,11 @@ func (s ConfirmationBlockObject) validateType() MessageObjectType {
 	return motConfirmation
 }
 
+// add styling to confirmation object
+func (s *ConfirmationBlockObject) WithStyle(style Style) {
+	s.Style = style
+}
+
 // NewConfirmationBlockObject returns an instance of a new Confirmation Block Object
 func NewConfirmationBlockObject(title, text, confirm, deny *TextBlockObject) *ConfirmationBlockObject {
 	return &ConfirmationBlockObject{