feat(code): add copy button for code (#239)

assets/svg/version.template.svg

@@ -0,0 +1,19 @@
+{{- /* https://img.shields.io/badge/$label-$version-$color?style=flat-square&labelColor=403c3d */ -}}
+{{- $labelLength := strings.RuneCount .label | mul 60 | add 120 -}}
+{{- $versionLength := strings.RuneCount .version | mul 60 -}}
+<svg xmlns="http://www.w3.org/2000/svg" width="{{ add $labelLength $versionLength | add 200 | mul 0.1 }}" height="20">
+    <g shape-rendering="crispEdges">
+        {{- $x1 := add $labelLength 100 | mul 0.1 -}}
+        {{- $x2 := add $versionLength 100 | mul 0.1 -}}
+        <path fill="#403c3d" d="M0 0h{{ $x1 }}v20H0z"/>
+        <path fill="#{{ .color }}" d="M{{ $x1 }} 0h{{ $x2 }}v20H{{ $x1 }}z"/>
+    </g>
+    <g fill="#fff" text-anchor="middle" font-family="DejaVu Sans,Verdana,Geneva,sans-serif" font-size="110">
+        <text x="{{ div $labelLength 2 | add 60 }}" y="140" textLength="{{ $labelLength }}" transform="scale(.1)">
+            {{- .label -}}
+        </text>
+        <text x="{{ div $versionLength 2 | add $labelLength | add 140 }}" y="140" textLength="{{ $versionLength }}" transform="scale(.1)">
+            {{- .version -}}
+        </text>
+    </g>
+</svg>