initial atari tests (not with image) and dither improvements

palette selection now biases to matches on the bright side of
the RGB color cube, since black is always available for dithering

does better but still not perfect

atari binary just writes some test data to text framebuffer
but builds and runs

dither4.s

@@ -0,0 +1,23 @@
+SAVMSC = $58
+
+.code
+
+.export start
+
+.proc start
+    ; Get the framebuffer address and just write new fun values into it
+    ; x: byte to write in
+    ; y: index into the first 256 bytes of buffer
+
+    ldx #00
+outer_loop:
+    txa
+    ldy #00
+inner_loop:
+    sta (SAVMSC),y
+    iny
+    bne inner_loop
+    inx
+    jmp outer_loop
+    ; infinite loop
+.endproc