Update vendor (#1228)

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

@@ -0,0 +1,38 @@
+package slack
+
+// HeaderBlock defines a new block of type header
+//
+// More Information: https://api.slack.com/reference/messaging/blocks#header
+type HeaderBlock struct {
+	Type    MessageBlockType `json:"type"`
+	Text    *TextBlockObject `json:"text,omitempty"`
+	BlockID string           `json:"block_id,omitempty"`
+}
+
+// BlockType returns the type of the block
+func (s HeaderBlock) BlockType() MessageBlockType {
+	return s.Type
+}
+
+// HeaderBlockOption allows configuration of options for a new header block
+type HeaderBlockOption func(*HeaderBlock)
+
+func HeaderBlockOptionBlockID(blockID string) HeaderBlockOption {
+	return func(block *HeaderBlock) {
+		block.BlockID = blockID
+	}
+}
+
+// NewHeaderBlock returns a new instance of a header block to be rendered
+func NewHeaderBlock(textObj *TextBlockObject, options ...HeaderBlockOption) *HeaderBlock {
+	block := HeaderBlock{
+		Type: MBTHeader,
+		Text: textObj,
+	}
+
+	for _, option := range options {
+		option(&block)
+	}
+
+	return &block
+}