New: Darkmode

* New: Native Theme Engine

Co-Authored-By: Zak Saunders <thezak48@users.noreply.github.com>
(cherry picked from commit 2291f3e00eb2ff9268a0b2f49da8dde82ee13c04)

* Update CSS for themes

* Fixup CSS values

* Fixup remove duped Color-Impaired setting

* Fixup Link Colors

Co-Authored-By: Qstick <qstick@gmail.com>

frontend/src/InteractiveImport/Author/SelectAuthorRow.css

@@ -1,4 +1,4 @@
 .author {
   padding: 8px;
-  border-bottom: 1px solid $borderColor;
+  border-bottom: 1px solid var(--borderColor);
 }

frontend/src/InteractiveImport/Interactive/InteractiveImportModalContent.css

@@ -35,7 +35,7 @@
 }
 
 .errorMessage {
-  color: $dangerColor;
+  color: var(--dangerColor);
 }
 
 @media only screen and (max-width: $breakpointSmall) {

frontend/src/InteractiveImport/Interactive/InteractiveImportRow.css

@@ -26,5 +26,5 @@
 .additionalFile {
   composes: row from '~Components/Table/TableRow.css';
 
-  color: $disabledColor;
+  color: var(--disabledColor);
 }

frontend/src/InteractiveImport/Interactive/InteractiveImportRowCellPlaceholder.css

@@ -3,5 +3,5 @@
   margin: -8px 0;
   width: 100%;
   height: 25px;
-  border: 2px dashed $dangerColor;
+  border: 2px dashed var(--dangerColor);
 }