Update SCSS to module system (fixes #266)

Change-Id: I2387ef49dadaeac0f62620e0c803df12dad42cf8
diff --git a/dev/scss/header/panel.scss b/dev/scss/header/panel.scss
index 459ab2b..e0fe6c6 100644
--- a/dev/scss/header/panel.scss
+++ b/dev/scss/header/panel.scss
@@ -1,11 +1,13 @@
-@import "../util";
+@use "../util";
+@use "../base/colors";
+@use "../base/lengths";
 
 // In addition to main/panel.scss
 
 div.panel.query div.view {
-  background-color: $dark-green;
-  border-left: $border-size solid $dark-green;
+  background-color: colors.$dark-green;
+  border-left: lengths.$border-size solid colors.$dark-green;
   iframe {
-    background-color: $nearly-white;
+    background-color: colors.$nearly-white;
   }
 }