An extra option is added in order to have control over the paddings.
Snippets using the `px-3` class have had it replaced with inline styles
and now have the padding option in the builder.
This was initially done for the media_list snippet, but it seems it's
useful for many more snippets.
Part-of: odoo/odoo#95940
Replace bootstrap classes by inline styles.
Added a <p> around the ENDOFSUMMER20 text so it can be edited with the
design-tab along with other text.
A `.o_mail_no_margin` class is added to the <p> element otherwise the
text isn't vertically centered inside the the table cell.
Part-of: odoo/odoo#95940