style/pdf viewer: add support for background effects

Author: adoriandoran

apps/client/src/stylesheets/theme-next/base.css

@@ -17,6 +17,8 @@
  */
 
 :root {
+    color-scheme: light dark;
+
     --main-font-family: "Inter", sans-serif;
 
     --main-font-size: normal;

packages/pdfjs-viewer/src/custom.css

@@ -1,7 +1,9 @@
 :root {
+    color-scheme: light dark;
+    
+    --body-bg-color: transparent;
+    --toolbar-bg-color: transparent;
     --main-color: var(--tn-main-text-color);
-    --body-bg-color: var(--tn-main-background-color);
-    --toolbar-bg-color: var(--tn-main-background-color);
     --toolbar-border-color: var(--tn-main-border-color);
     --toolbar-icon-opacity: 1;
 }