[FIX] web_editor: re-encourage to use snippets in empty oe_structure

This commit re-applies the commit that was merged at [1] but whose
code was lost during Jabberwock revert at [2].

Make the draggable snippets "wizz" when the user clicks on an empty
oe_structure.

[1]: https://github.com/odoo/odoo/commit/3ed3537abd416ebc35f8bc2ee65f209840c071bf
[2]: https://github.com/odoo/odoo/commit/e5572c317a7775a58675ed73efc89b5c9f6c0c39

Related to task-2363616

closes odoo/odoo#82046

X-original-commit: 668539aa17f061c8851099863e4d5fb7b11b59e8
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/web_editor/static/src/js/editor/snippets.editor.js

@@ -1300,6 +1300,13 @@ var SnippetsMenu = Widget.extend({
             if ($target.closest(this._notActivableElementsSelector).length) {
                 return;
             }
+            const $oeStructure = $target.closest('.oe_structure');
+            if ($oeStructure.length && !$oeStructure.children().length && this.$snippets) {
+                // If empty oe_structure, encourage using snippets in there by
+                // making them "wizz" in the panel.
+                this.$snippets.odooBounce();
+                return;
+            }
             this._activateSnippet($target);
         };