Added theming support for gitgraph

cypress/platform/gitgraph.html

@@ -9,7 +9,8 @@
     <style>
       body {
         /* background: rgb(221, 208, 208); */
-        /*background:#333;*/
+        background:#111;
+        /* background:#333; */
         font-family: 'Arial';
         }
       /* h1 { color: white;} */
@@ -103,6 +104,20 @@
       };
       mermaid.initialize({
         theme: 'base',
+        themeVariables: {
+          primaryColor: '#9400D3',
+          darkMode: true,
+          // background: '#222',
+          textColor: 'white',
+          primaryTextColor: '#f4f4f4',
+
+          // nodeBkg: '#ff0000',
+          // mainBkg: '#0000ff',
+          // tertiaryColor: '#ffffcc',
+        },
+        // theme: 'forest',
+        // theme: 'neutral',
+        // theme: 'dark',
         // arrowMarkerAbsolute: true,
         // themeCSS: '.edgePath .path {stroke: red;} .arrowheadPath {fill: red;}',
         logLevel: 1,