Added highlight to markdown code. Added markdown icon to differentiate against markdown on/off.

static/images/markdown-hollow.svg

@@ -0,0 +1,49 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg
+   height="128"
+   width="208"
+   viewBox="-31.2 -32 208 128"
+   version="1.1"
+   id="svg1"
+   sodipodi:docname="markdown-hollow.svg"
+   inkscape:version="1.3.2 (1:1.3.2+202311252150+091e20ef0f)"
+   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="true"
+     inkscape:deskcolor="#d1d1d1"
+     inkscape:zoom="5.6568542"
+     inkscape:cx="109.68994"
+     inkscape:cy="68.942911"
+     inkscape:window-width="1916"
+     inkscape:window-height="1404"
+     inkscape:window-x="1280"
+     inkscape:window-y="16"
+     inkscape:window-maximized="1"
+     inkscape:current-layer="svg1" />
+  <rect
+     fill="none"
+     stroke-width="10"
+     stroke="#000000"
+     ry="10"
+     y="-27"
+     x="-26.200001"
+     height="118"
+     width="198"
+     id="rect1"
+     style="stroke:#ffffff;stroke-opacity:1" />
+  <path
+     d="M -1.2000003,66 V -2 H 18.8 l 20,25 20,-25 h 20 v 68 h -20 V 27 l -20,25 -20,-25 V 66 Z M 123.8,66 93.8,33 h 20 V -2 h 20 v 35 h 20 z"
+     id="path1"
+     style="fill:#ffffff;fill-opacity:1" />
+</svg>