fix(material/datepicker): expose datepicker-date-range-colors mixin

Exposes the `datepicker-date-range-colors` mixin which seems to be not
accessible in the primary Sass entry-point, but being mentioned in the docs.

Author: devversion

src/material/_index.scss

@@ -49,7 +49,7 @@
   checkbox-typography;
 @forward './chips/chips-theme' as chips-* show chips-theme, chips-color, chips-typography;
 @forward './datepicker/datepicker-theme' as datepicker-* show datepicker-theme, datepicker-color,
-  datepicker-typography;
+  datepicker-typography, datepicker-date-range-colors;
 @forward './dialog/dialog-theme' as dialog-* show dialog-theme, dialog-color, dialog-typography;
 @forward './divider/divider-theme' as divider-* show divider-theme, divider-color,
   divider-typography;

src/material/datepicker/datepicker.md

@@ -230,7 +230,14 @@ selected range.
 
 Note that comparison and overlap colors aren't derived from the current theme, due
 to limitations in the Material Design theming system. They can be customized using the
-`mat-date-range-colors` mixin.
+`datepicker-date-range-colors` mixin.
+
+```scss
+@use '@angular/material' as mat;
+
+@include mat.datepicker-date-range-colors(
+  hotpink, teal, yellow, purple);
+```
 
 ### Customizing the date selection logic