[IMP] Add image option to cards, update guidelines

[fw-bot]

Summary:

Extends the custom Card RST directive to allow for images and alt text based on bootstrap conventions. Added an example in the guidelines and tweaked layout javascript to make card images render correctly.

Task: https://www.odoo.com/odoo/project/3835/tasks/6393116

 .. card:: Card with image
                :target: ../documentation
                :large:
                :image: placeholder-card-image.png
                :alt: Placeholder card image

                Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor.

This 17.0 PR can be FWP up to master.

Forward-Port-Of: #18946

[robodoo]

[fw-bot]

@nikibrown @Felicious this PR targets master and is the last of the forward-port chain containing:

• [IMP] Add image option to cards, update guidelines #19140
• [IMP] Add image option to cards, update guidelines #19139
• [IMP] Add image option to cards, update guidelines #19137
• [IMP] Add image option to cards, update guidelines #19136
• [IMP] Add image option to cards, update guidelines #19135
• [IMP] Add image option to cards, update guidelines #19133
• [IMP] Add image option to cards, update guidelines #19132
• [IMP] Add image option to cards, update guidelines #19131

To merge the full chain, use

@robodoo r+

More info at https://github.com/odoo/odoo/wiki/Mergebot#forward-port