YITH WooCommerce Brands 2.28.0

* New: WooCommerce 3.6.0 RC1 support
* Update: Spanish language
* Update: internal plugin framework
* Dev: added new filter yith_wcbr_brand_taxonomy_columns
* Dev: added new filter yith_wcbr_brand_taxonomy_column
* Dev: added new filter yith_wcbr_image_size_single_product_brads
* Dev: added new filter yith_wcbr_thumbnail_image on thumbnail carousel shortcode

New: WooCommerce 3.5.4 support
New: added brands to product structured data
Tweak: brands are now correctly added to the new product, when duplicating an existing one
Update: Italian language
Updated: Dutch language
Update: internal plugin framework
Fix: preventing warning when trying to explode an array
Fix: preventing notices caused by undefined indexes
Dev: added filter yith_wcbr_product_filter_by_brand_args
Dev: added yith_wcbr_get_terms_args filter

New: WordPress 5.0 support
New: WooCommerce 3.5.2 support
New: added Gutenberg blocks for plugin shortcodes
New: added pagination param to Brand Thumbnail widget
Update: dutch language
Fix: hide empty filter not being removed after get_terms
Dev: added filter yith_wcbr_thumbnail_carrousel_shortcode_atts