[IMP] website, *: expand click handler on theme color palettes

*: web_editor

The goal of this commit is make the whole we-collapse elements
clickable for theme color palettes.

Part of https://github.com/odoo/odoo/pull/68061
task-2431484

addons/web_editor/static/src/scss/wysiwyg_snippets.scss

@@ -1557,6 +1557,9 @@ body.editor_enable.editor_has_snippets {
                     background-color: $o-we-bg-lighter;
                 }
             }
+            .o_we_collapse_toggler {
+                cursor: pointer;
+            }
         }
 
         .o_we_image_weight {

addons/website/static/src/js/editor/snippets.options.js

@@ -1245,7 +1245,7 @@ options.registry.ThemeColors = options.registry.OptionsTab.extend({
         for (let i = 1; i <= 5; i++) {
             const collapseEl = document.createElement('we-collapse');
             const ccPreviewEl = $(qweb.render('web_editor.color.combination.preview'))[0];
-            ccPreviewEl.classList.add('text-center', `o_cc${i}`);
+            ccPreviewEl.classList.add('text-center', `o_cc${i}`, 'o_we_collapse_toggler');
             collapseEl.appendChild(ccPreviewEl);
             const editionEls = $(qweb.render('website.color_combination_edition', {number: i}));
             for (const el of editionEls) {