Using color-scheme and light-dark() to implement dark mode (#154)

* Lint fixes.

* Implement light-dark().

* Lint css with biome, remove stylelint.

* Biome lint fixes.

* Dark mode adjustments.

* Style bug fixes.

* Colour adjustments.

* Move header and footer styles to base.

* Site header adjustments.

* Removing jQuery and umbrella libs. They where great but not needed anymore.

* Add colorScheme to optionally lock light/dark.

* Update README.

* Biome adjustments.

assets/css/components/_cookieconsent.css

@@ -4,7 +4,7 @@
   display: flex;
   flex-flow: wrap;
   justify-content: center;
-  gap: .5rem;
+  gap: 0.5rem;
   position: sticky;
   bottom: 0;
   width: 100%;
@@ -19,7 +19,7 @@
 
   .cookieconsent__actions {
     display: flex;
-    gap: .5rem;
+    gap: 0.5rem;
   }
 
   &[hidden] {