[NTG-context] Add labels to a grid (Metafun)

[Fabrice]

thank you very much Alain, I think I understood for the format "@d" but 
for other formats, I will need documentation.
Fabrice

\definecolor[mycolor][c=.4,m=0,y=0,k=0]

\starttext
\start
\switchtobodyfont[small]
\startMPcode
      xmin := 0; xmax := 22; ymax :=460 ;ymin:=0; u := 0.5cm; v:= 0.025cm;
      drawoptions(withpen pencircle scaled 0.5pt withcolor 
\MPcolor{mycolor});
      draw hlingrid(ymin,ymax,20,11.5cm,11cm);
      draw vlingrid(xmin,xmax,2,11cm,11.5cm);
      drawoptions(withpen pencircle scaled 1pt) ;
      drawarrow (0,0)--(22,0) scaled u ;
      drawarrow (0,0)--(0,460) scaled v ;
      draw vlintext(0,20,2,10cm,"@d") shifted (0,-0.25cm) ;
      draw hlintext(0,420,20,11cm,"@d") shifted (-0.35cm,0) ;
      label.bot( "$x$",(10.8cm,-0.1cm)) ;
      label.lft( "$y$",(-0.1cm,11.4cm)) ;
\stopMPcode
\stop
\stoptext