[FIX] web_editor: fix user avatar aspect-ratio

This commit fixes an issue occurring in the `web_editor` when multiple
users edit some content.

Prior to this commit, the user avatar was not using any aspect-ratio
rule, resulting in a stretch avatar if the uploaded image wasn't square.

This commit fixes this issue by adding the `o_object_fit_cover` class to
the image, ensuring a correct ratio no matter the format of the uploaded
image.

task-3877841

closes odoo/odoo#162810

X-original-commit: 7240fa3ff495a8aba7bd53b720e99cd767948342
Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>
Signed-off-by: Chrysanthe Gomrée (chgo) <chgo@odoo.com>

addons/web_editor/static/src/js/editor/odoo-editor/src/OdooEditor.js

@@ -1954,6 +1954,7 @@ export class OdooEditor extends EventTarget {
             avatarElement.append(image);
             image.onload = () => avatarElement.style.removeProperty('display');
             image.setAttribute('src', clientAvatarUrl);
+            image.classList.add('o_object_fit_cover');
         }
         // Avoid re-appending the element in the dom.
         if (!avatarElement.parentElement) {