added plotting of pattern

[SReich-EMI]

added a function to directly plot the stitching pattern. Only reading out the color hex code I didn't find. Added therefore a TODO Would be nice if this could be added.

[tatarize]

There are no dependencies for pyembroidery. The only way this could be accepted is if the imports were put in the function and caught the import error within that function. I don't have a major objection to soft dependencies but hard dependencies aren't a thing that will ever be part of this library.

If you want to see this to a weird level look at the PNG writer, it's coded up barebones rather than half a dozen lines of Pillow referenced code.

[tatarize]

    from PIL import Image, ImageDraw
    extends = pattern.bounds()
    pattern.translate(-extends[0], -extends[1])
    width = int(extends[2] - extends[0])
    height = int(extends[3] - extends[1])
    draw_buff = Image.new('RGBA', (width, height))
    drawer = ImageDraw.Draw(draw_buff)
    for stitches, color in pattern.get_as_stitchblock():
        if len(stitches) == 0:
            continue
        b = [(q[0], q[1]) for q in stitches]
        drawer.line(b, fill=color.hex_color(), width=3)

The stitch block gives the color for that stitchblock too.