feat: Replace == with <mark> (#234)

Co-authored-by: SAF <saf@saf.saf>

assets/styles/base.scss

@@ -619,3 +619,7 @@ header {
   }
 }
 
+mark {
+  background-color: var(--highlighted);
+  color: var(--gray);
+}

assets/styles/custom.scss

@@ -11,6 +11,7 @@
   --lightgray: #f0f0f0;
   --outlinegray: #dadada;
   --million-progress-bar-color: var(--secondary);
+  --highlighted: #f5dfaf88;
 }
 
 [saved-theme="dark"] {
@@ -23,6 +24,7 @@
   --gray: #d4d4d4 !important;
   --lightgray: #292633 !important;
   --outlinegray: #343434 !important;
+  --highlighted: #574010;
 }