Update dependencies for 1.18.0 release (#1175)

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

@@ -2,6 +2,7 @@ package slack
 
 import (
 	"encoding/json"
+	"fmt"
 
 	"github.com/pkg/errors"
 )
@@ -172,10 +173,12 @@ func (b *BlockElements) UnmarshalJSON(data []byte) error {
 			blockElement = &DatePickerBlockElement{}
 		case "plain_text_input":
 			blockElement = &PlainTextInputBlockElement{}
+		case "checkboxes":
+			blockElement = &CheckboxGroupsBlockElement{}
 		case "static_select", "external_select", "users_select", "conversations_select", "channels_select":
 			blockElement = &SelectBlockElement{}
 		default:
-			return errors.New("unsupported block element type")
+			return fmt.Errorf("unsupported block element type %v", blockElementType)
 		}
 
 		err = json.Unmarshal(r, blockElement)
@@ -275,6 +278,12 @@ func (a *Accessory) UnmarshalJSON(data []byte) error {
 			return err
 		}
 		a.MultiSelectElement = element.(*MultiSelectBlockElement)
+	case "checkboxes":
+		element, err := unmarshalBlockElement(r, &CheckboxGroupsBlockElement{})
+		if err != nil {
+			return err
+		}
+		a.CheckboxGroupsBlockElement = element.(*CheckboxGroupsBlockElement)
 	default:
 		element, err := unmarshalBlockElement(r, &UnknownBlockElement{})
 		if err != nil {
@@ -313,6 +322,9 @@ func toBlockElement(element *Accessory) BlockElement {
 	if element.RadioButtonsElement != nil {
 		return element.RadioButtonsElement
 	}
+	if element.CheckboxGroupsBlockElement != nil {
+		return element.CheckboxGroupsBlockElement
+	}
 	if element.SelectElement != nil {
 		return element.SelectElement
 	}