I am currently using Mercury 2.2 with the WYSIWYG setting and I am new to Publii. I want to insert code into the <head> of every page. As the site grows I’ll be looking at Google Adsense (maybe), Shopify and possibly some other scripts. They will need to some script inserted into the <HEAD> tag. I can’t seem to do this through the theme. Is there an easy approach to getting code into the Head tag?