fix(docs): watermark example

README.md

@@ -185,8 +185,7 @@ if err != nil {
   fmt.Fprintln(os.Stderr, err)
 }
 
-options := bimg.Watermark{
+watermark := bimg.Watermark{
-  Watermark{
   Text:       "Chuck Norris (c) 2315",
   Opacity:    0.25,
   Width:      200,
@@ -194,10 +193,9 @@ options := bimg.Watermark{
   Margin:     150,
   Font:       "sans bold 12",
   Background: bimg.Color{255, 255, 255},
-  }
 }
 
-newImage, err := bimg.NewImage(buffer).Watermark(options)
+newImage, err := bimg.NewImage(buffer).Watermark(watermark)
 if err != nil {
   fmt.Fprintln(os.Stderr, err)
 }