update vendor

vendor/github.com/cpuguy83/go-md2man/v2/md2man/md2man.go

@@ -1,14 +1,24 @@
+// Package md2man aims in converting markdown into roff (man pages).
 package md2man
 
 import (
+	"os"
+	"strconv"
+
 	"github.com/russross/blackfriday/v2"
 )
 
 // Render converts a markdown document into a roff formatted document.
 func Render(doc []byte) []byte {
 	renderer := NewRoffRenderer()
+	var r blackfriday.Renderer = renderer
+	if v, _ := strconv.ParseBool(os.Getenv("MD2MAN_DEBUG")); v {
+		r = &debugDecorator{Renderer: r}
+	}
 
 	return blackfriday.Run(doc,
-		[]blackfriday.Option{blackfriday.WithRenderer(renderer),
-			blackfriday.WithExtensions(renderer.GetExtensions())}...)
+		[]blackfriday.Option{
+			blackfriday.WithRenderer(r),
+			blackfriday.WithExtensions(renderer.GetExtensions()),
+		}...)
 }