graphviz: make the diagrams' background transparent by default

No need to set a background color, is there?

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

assets/sass/layout.scss

@@ -317,6 +317,10 @@ p.center {
   }
 }
 
+svg.graphviz {
+  width: 100%;
+}
+
 // Dropdowns
 a.dropdown-trigger {
   padding: 4px 5px;

layouts/_default/baseof.html

@@ -198,7 +198,12 @@ <h1 data-pagefind-meta="title">About{{ if (isset .Params "subtitle") }} - {{ .Pa
     let vizInstance
     [...document.querySelectorAll("pre[class=graphviz]")].forEach(async (x) => {
       if (!vizInstance) vizInstance = await Viz.instance()
-      const svg = vizInstance.renderSVGElement(x.innerText)
+      const options = {
+        graphAttributes: {
+          bgcolor: "transparent",
+        },
+      }
+      const svg = vizInstance.renderSVGElement(x.innerText, options)
       x.parentNode.insertBefore(svg, x);
       x.style.display = 'none'
     });