No valid HTML output

[wschwaiger]

Please describe the feature you would like to see implemented.

The plugin does not produce valid HTML code and does not pass the validator test under https://validator.w3.org/

Changes need to be made in the product-image.tpl by adding src="{$sArticle.image.source}" in line 10. The error originated in Shopware itself.

[shyim]

Can you make a PR?