show: make highlight legible

fixes #125

cmd/dcs-web/templates/show.html

@@ -52,7 +52,7 @@
 <h2>Source of {{.filename}}</h2>
 
 <!-- Line numbers on the left of the source code -->
-<div class="lnr"><pre>{{range $idx, $line := .numbers}}{{ if eq $line $.line }}<span style="font-weight: bold; background-color: #333;">{{ end }}<a id="L{{$line}}"><span id="L{{$line}}"></a>{{$line}}</span>{{ if eq $line $.line }}</span>{{ end }}
+<div class="lnr"><pre>{{range $idx, $line := .numbers}}{{ if eq $line $.line }}<span style="font-weight: bold; background-color: #333; color: #fff">{{ end }}<a id="L{{$line}}"><span id="L{{$line}}"></a>{{$line}}</span>{{ if eq $line $.line }}</span>{{ end }}
 {{end}}
 </pre></div>
 <!-- The source code itself -->