YITH WooCommerce Barcodes and QR Codes Premium 2.34.0

* Update: Updated plugin FW
* Tweak: Check if the Pelago/Emogrifier class exist
* Dev: Filter yith_ywbc_barcode_image_tag

* New: support to WooCommerce 3.6.0 RC 1
* Tweak: changes in the plugin settings to improve the usability
* Update: updated plugin FW
* Fix: fixed Trying to get property 'display_name' of non-object
* Dev: added a new filter in the frontend JS enqueue
* Dev: added the Pelago namespace to the Emogrifier class call

Update: updated plugin FW
Update: updated Italian language
Update: updated Dutch language
Update: updated Spanish language
Fix: text domain for some string
Fix: string localization
Fix: fixed the manual barcode option in product page