pngcheck: add Dutch translation and fix placeholder (#13648)

pages/common/pngcheck.md

@@ -5,15 +5,15 @@
 
 - Print a summary for an image (width, height, and color depth):
 
-`pngcheck {{image.png}}`
+`pngcheck {{path/to/image.png}}`
 
 - Print information for an image with [c]olorized output:
 
-`pngcheck -c {{image.png}}`
+`pngcheck -c {{path/to/image.png}}`
 
 - Print [v]erbose information for an image:
 
-`pngcheck -cvt {{image.png}}`
+`pngcheck -cvt {{path/to/image.png}}`
 
 - Receive an image from `stdin` and display detailed information:
 
@@ -21,8 +21,8 @@
 
 - [s]earch for PNGs within a specific file and display information about them:
 
-`pngcheck -s {{image.png}}`
+`pngcheck -s {{path/to/image.png}}`
 
 - Search for PNGs within another file and e[x]tract them:
 
-`pngcheck -x {{image.png}}`
+`pngcheck -x {{path/to/image.png}}`