fix(themes): enforce foreground as a required variant

Author: brandyscarney

core/src/css/palettes/dark.scss

@@ -86,6 +86,7 @@ $colors: (
       --ion-color-#{$color-name}-contrast-rgb: #{color-to-rgb-list(map.get($value, contrast))};
       --ion-color-#{$color-name}-shade: #{map.get($value, shade)};
       --ion-color-#{$color-name}-tint: #{map.get($value, tint)};
+      --ion-color-#{$color-name}-foreground: #{map.get($value, foreground)};
     }
   }
 }

core/src/css/palettes/high-contrast-dark.scss

@@ -113,6 +113,7 @@ $lightest-text-color: $text-color;
       --ion-color-#{$color-name}-contrast-rgb: #{color-to-rgb-list(map.get($value, contrast))};
       --ion-color-#{$color-name}-shade: #{map.get($value, shade)};
       --ion-color-#{$color-name}-tint: #{map.get($value, tint)};
+      --ion-color-#{$color-name}-foreground: #{map.get($value, foreground)};
     }
   }
 }

core/src/css/palettes/high-contrast.scss

@@ -136,6 +136,7 @@ $lightest-text-color: #888888;
       --ion-color-#{$color-name}-contrast-rgb: #{color-to-rgb-list(map.get($value, contrast))};
       --ion-color-#{$color-name}-shade: #{map.get($value, shade)};
       --ion-color-#{$color-name}-tint: #{map.get($value, tint)};
+      --ion-color-#{$color-name}-foreground: #{map.get($value, foreground)};
     }
   }
 }