Fix dark mode scrollbars

source/electron.html

@@ -69,6 +69,7 @@ button { font-family: -apple-system, BlinkMacSystemFont, "Segoe WPC", "Segoe UI"
 .default .graph { display: block; opacity: 1; }
 .default .toolbar { display: table; }
 @media (prefers-color-scheme: dark) {
+:root { color-scheme: dark; }
 .default { background-color: #404040; }
 .graph { background-color: #404040; }
 .welcome { background-color: #1e1e1e; color: #888888; }

source/index.html

@@ -116,6 +116,7 @@ button { font-family: -apple-system, BlinkMacSystemFont, "Segoe WPC", "Segoe UI"
 .default .graph { display: block; opacity: 1; }
 .default .toolbar { display: table; }
 @media (prefers-color-scheme: dark) {
+:root { color-scheme: dark; }
 .default { background-color: #404040; }
 .graph { background-color: #404040; }
 .about { background-color: #404040; }