update example gallery

<h1>Example: <code>{{example_url}}</code></h1>

<h4>Output File:</h4>

<a href="/examples/{{example_url}}.svg" target="_blank"><img src="/examples/{{example_url}}.svg" /></a>

<p style="text-align: center;">

  <img style="max-width: 80%;" src="/examples/{{example_url}}.svg" />

</p>

<h4>Source File:</h4>

<pre><code>{{example_src}}</code></pre>

(width 2048px)

(height 512px)

(width 1600px)

(height 900px)

(dpi 240)

(default scale-x (categorical (A B C D E F)))

(width 2048px)

(height 512px)

(width 1600px)

(height 800px)

(dpi 240)

(default font "Comic Sans MS")

    position (bottom left)

    label-format-y (fixed 2)

    label-format-x (datetime "%H:%M:%S")

    label-placement-x (linear 3600)

    label-placement-y (linear 20))

(draw/rectangle

    fill #f2f2f2)

(plot/grid

    color #fff)

(plot/lines

    data-x (csv "test/testdata/measurement.csv" time)

    data-y (csv "test/testdata/measurement.csv" value2))