Add a background graphic;

Add more information to the file README.

img/background.svg

@@ -0,0 +1,45 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!-- Created with Inkscape (http://www.inkscape.org/) -->
+
+<svg
+   version="1.1"
+   id="svg1"
+   width="80"
+   height="92"
+   viewBox="0 0 80 92"
+   sodipodi:docname="background_0004.svg"
+   inkscape:version="1.3.2 (091e20ef0f, 2023-11-25, custom)"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:svg="http://www.w3.org/2000/svg">
+  <defs
+     id="defs1" />
+  <sodipodi:namedview
+     id="namedview1"
+     pagecolor="#ffffff"
+     bordercolor="#666666"
+     borderopacity="1.0"
+     inkscape:showpageshadow="2"
+     inkscape:pageopacity="0.0"
+     inkscape:pagecheckerboard="0"
+     inkscape:deskcolor="#d1d1d1"
+     inkscape:zoom="5.9"
+     inkscape:cx="39.830508"
+     inkscape:cy="47.033898"
+     inkscape:window-width="1916"
+     inkscape:window-height="1032"
+     inkscape:window-x="0"
+     inkscape:window-y="22"
+     inkscape:window-maximized="1"
+     inkscape:current-layer="g1" />
+  <g
+     inkscape:groupmode="layer"
+     inkscape:label="Image"
+     id="g1">
+    <path
+       style="fill:none;stroke:#dadada"
+       d="M 7.9933697,3.8536538e-4 C 8.0070897,20.71715 22.520416,14.85765 32.522174,28.28434 c 3.71128,4.98214 2.20517,13.84718 2.13272,19.71605 C 34.426664,66.48723 19.361635,62.39385 10.131229,73.8543 6.4409207,78.43618 7.9933697,86.63903 7.9933697,92.0004 M 71.993374,3.8536538e-4 C 71.978074,19.85167 56.686694,14.9665 47.464564,28.1403 c -4.0466,5.78057 -2.40551,17.09222 -2.11214,23.86009 0.62031,14.31026 16.82256,13.46918 24.50308,22.18312 3.72915,4.23091 2.13787,12.56287 2.13787,17.81689"
+       id="path1" />
+  </g>
+</svg>