docs: Change Kinematics.md images to use a solid white background

Avoid transparent backgrounds as they don't render well if there is a
dark background.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

docs/img/zigzag.svg

@@ -2,20 +2,23 @@
 <!-- Created with Inkscape (http://www.inkscape.org/) -->
 
 <svg
-   xmlns:dc="http://purl.org/dc/elements/1.1/"
-   xmlns:cc="http://creativecommons.org/ns#"
-   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
-   xmlns:svg="http://www.w3.org/2000/svg"
-   xmlns="http://www.w3.org/2000/svg"
-   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
-   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
    width="97.22496mm"
    height="32.550285mm"
    viewBox="0 0 344.49789 115.33566"
    id="svg2"
    version="1.1"
-   inkscape:version="0.91 r13725"
-   sodipodi:docname="zigzag.svg">
+   inkscape:version="1.1 (c68e22c387, 2021-05-23)"
+   sodipodi:docname="zigzag.svg"
+   inkscape:export-filename="/home/kevin/src/reprap/firmware/klipper/docs/img/zigzag.svg.png"
+   inkscape:export-xdpi="90"
+   inkscape:export-ydpi="90"
+   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"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:dc="http://purl.org/dc/elements/1.1/">
   <defs
      id="defs4" />
   <sodipodi:namedview
@@ -23,15 +26,15 @@
      pagecolor="#ffffff"
      bordercolor="#666666"
      borderopacity="1.0"
-     inkscape:pageopacity="0.0"
+     inkscape:pageopacity="1"
      inkscape:pageshadow="2"
      inkscape:zoom="1.75"
-     inkscape:cx="167.32577"
-     inkscape:cy="45.708959"
+     inkscape:cx="346.28571"
+     inkscape:cy="46"
      inkscape:document-units="px"
      inkscape:current-layer="layer1"
      showgrid="false"
-     inkscape:window-width="840"
+     inkscape:window-width="1031"
      inkscape:window-height="628"
      inkscape:window-x="160"
      inkscape:window-y="35"
@@ -42,7 +45,8 @@
      fit-margin-bottom="0"
      showborder="false"
      inkscape:snap-global="false"
-     showguides="false">
+     showguides="false"
+     inkscape:pagecheckerboard="0">
     <inkscape:grid
        type="xygrid"
        id="grid3436" />
@@ -55,7 +59,6 @@
         <dc:format>image/svg+xml</dc:format>
         <dc:type
            rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
-        <dc:title></dc:title>
       </cc:Work>
     </rdf:RDF>
   </metadata>
@@ -72,27 +75,27 @@
        sodipodi:nodetypes="cccc" />
     <text
        xml:space="preserve"
-       style="font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;font-size:12.5px;line-height:100%;font-family:'DejaVu Sans';-inkscape-font-specification:'DejaVu Sans, Normal';text-align:start;letter-spacing:0px;word-spacing:0px;writing-mode:lr-tb;text-anchor:start;fill:#000000;fill-opacity:1;stroke:none;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"
+       style="font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;line-height:0%;font-family:'DejaVu Sans';-inkscape-font-specification:'DejaVu Sans, Normal';text-align:start;letter-spacing:0px;word-spacing:0px;writing-mode:lr-tb;text-anchor:start;fill:#000000;fill-opacity:1;stroke:none;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"
        x="434.04257"
        y="365.1282"
-       id="text3349"
-       sodipodi:linespacing="100%"><tspan
+       id="text3349"><tspan
          sodipodi:role="line"
          id="tspan3351"
          x="434.04257"
-         y="365.1282">time</tspan></text>
+         y="365.1282"
+         style="font-size:12.5px;line-height:1">time</tspan></text>
     <text
        xml:space="preserve"
-       style="font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;font-size:12.5px;line-height:125%;font-family:'DejaVu Sans';-inkscape-font-specification:'DejaVu Sans, Normal';text-align:start;letter-spacing:0px;word-spacing:0px;writing-mode:lr-tb;text-anchor:start;fill:#000000;fill-opacity:1;stroke:none;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"
+       style="font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;line-height:0%;font-family:'DejaVu Sans';-inkscape-font-specification:'DejaVu Sans, Normal';text-align:start;letter-spacing:0px;word-spacing:0px;writing-mode:lr-tb;text-anchor:start;fill:#000000;fill-opacity:1;stroke:none;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"
        x="-313.86618"
        y="140.27856"
        id="text3353"
-       sodipodi:linespacing="125%"
-       transform="matrix(-0.01601372,-0.99987177,0.99987177,-0.01601372,0,0)"><tspan
+       transform="rotate(-90.917558)"><tspan
          sodipodi:role="line"
          id="tspan3355"
          x="-313.86618"
-         y="140.27856">velocity</tspan></text>
+         y="140.27856"
+         style="font-size:12.5px;line-height:1.25">velocity</tspan></text>
     <path
        style="fill:none;fill-rule:evenodd;stroke:#000000;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1"
        d="m 150,250.23455 -5.31915,8.51063"