add the graphics book to the docs

HDISK/BASIC/GRTEST.BAS

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+10 DIM A(800)
+20 POKE 82,0:POKE 83,39
+25 REM ****************
+26 REM * USE PLOT, DRAWTO,
+27 REM * AND COLOR TO DRAW A 
+28 REM * "V" ON SCREEN
+29 REM *****************
+30 GRAPHICS 3
+40 COLOR 1:PLOT 0,0:DRAWTO 19,19
+50 COLOR 3:PLOT 39,0:DRAWTO 20,19
+60 POSITION 17,10:PRINT #6;"123123"
+95 REM *****************
+96 REM * STORES THE COLOR VALUES
+97 REM * PLOTTED EARLIER, SO WE CAN
+98 REM * PRINT THEM IN GR MODE 0
+99 REM *****************
+100 POSITION 0,0
+110 FOR I=1 TO 800
+120 GET #6,X
+130 A(I)=X
+140 NEXT I
+194 REM ************
+195 REM * NOW WE CAN OUTPUT THE ARRAY
+196 REM * AS VALUES, IN THE SAME
+197 REM * PATTERN AS THE PLOTTED
+198 REM * GRAPHICS EARLIER!
+199 REM ************
+200 GRAPHICS 0
+210 FOR I=1 TO 800
+220 PRINT A(I);
+230 NEXT I
+240 FOR J=1 TO 2000:NEXT J
+244 REM ***************
+245 REM * AND NOW WE CAN REDRAW THE
+246 REM * PATTERN USING PUT INSTEAD
+247 REM * OF PLOT AND DRAWTO
+248 REM * (A MUCH SLOWER PROCESS!)
+249 REM ***************
+300 GRAPHICS 3
+310 POSITION 0,0
+320 FOR I=1 TO 800
+330 PUT #6,A(I)
+340 NEXT I