fix(dueling-picklist): Add grow functionality to responsive variant (#4574)

Author: Alexis Córdova

RELEASENOTES.md

@@ -40,6 +40,10 @@
 #### Changed
 - Changed `flex-basis` to `auto` for the drop zone label to fix a layout issue in IE11
 
+### [Dueling Picklist](https://www.lightningdesignsystem.com/components/dueling-picklist)
+## Added
+- Responsive variant now grows to use up the available horizontal space.
+
 ### [Icons](https://www.lightningdesignsystem.com/components/icons)
 #### Changed
 - Changed `product_quantity_rules` icon's color from light blue to salem green (#04844B)
@@ -80,6 +84,7 @@
 #### Added
 - Added light and dark Brand variants, including new selectors `.slds-popover_brand, .slds-popover_brand-dark, .slds-popover_brand-top, .slds-popover_brand-left, .slds-popover_brand-bottom, .slds-popover_brand-right`
 - Added new Prompt branded variants
+- Enabled styling hooks for popovers. See popovers' styling hooks overview table for a full listing of the currently available hooks.
 
 ### [Rich Text Editor](https://www.lightningdesignsystem.com/components/rich-text-editor)
 #### Added

ui/components/dueling-picklist/RELEASENOTES.md

@@ -4,6 +4,12 @@
 
 <!-- ## [Unreleased] -->
 
+## 2.15.0
+
+## Added
+
+- Responsive variant now grows to use up the available horizontal space.
+
 ## 2.13.1
 
 ### Fixed

ui/components/dueling-picklist/base/_index.scss

@@ -45,7 +45,7 @@
  * @restrict .slds-dueling-list__column
  */
 .slds-dueling-list__column_responsive {
-  flex: 0 1 $size-small;
+  flex: 1 1 $size-small;
   flex-wrap: wrap;
   overflow: hidden;
   min-width: $size-xx-small;

ui/components/dueling-picklist/docs.mdx

@@ -77,7 +77,7 @@ A Dueling Picklist should have a group label, similar to using a `fieldset` and
 
 ## Responsive
 
-To make the dueling picklist responsive or use it within narrow regions, apply the class `slds-dueling-picklist__column_responsive` to the `<div>`s with class `slds-dueling-picklist__column` that contain options (not the columns that only contain buttons). Any items longer than the space available will truncate with ellipses.
+To make the dueling picklist responsive or use it within narrow regions, apply the class `slds-dueling-picklist__column_responsive` to the `<div>`s with class `slds-dueling-picklist__column` that contain options (not the columns that only contain buttons). The dueling picklist will take up all available horizontal space, and any items longer than the available space will truncate with an ellipsis.
 
 <Example title="Dueling Picklist Responsive">
   <CodeView>