[FIX] web_editor: support of SVG elements in snippets
[FIX] web_editor: support of SVG elements in snippets

Before this commit, it was not possible to save a page
containing a snippet with a SVG tag.

To support SVG elements, we need to use 'Element.getAttribute'
and 'Element.setAttribute' as mentionned in the documentation:
https://developer.mozilla.org/en-US/docs/Web/API/Element/className

For more information, see GH-14485

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo