Documentation: Clarify blend mode 'Writes to depth buffer' implications

While text is nice, a picture is worth a thousand words, and far more intuitive, especially for users that aren't super familiar with graphics terminology.

Specifically, for someone that isn't fairly familiar with graphics tech, the implications that stem from only the Opaque mode writing to the depth buffer, and how that relates to rendering order is not immediately obvious.

I think specifically this deserves a section that in one or two images very clearly illustrates what that means, namely that without writing to the depth buffer, lines drawn in immediate mode with Draw.Polylines or Draw.Line are draw-order specific, and you may see unexpected overlapping where lines that are far away will visually be drawn on top of lines that are closer to the camera, if the further lines were drawn later.

Edit: changed topic title to better reflect my original intent.