Add a "Properties using Folksonomy Engine" placeholder for "opf"

[teolemon]

What

• Add a "Properties using Folksonomy Engine" placeholder for Open Products Facts - "opf" in Edit Mode
• Plug it to the Webview of the product page, and to Add UI support for writing properties to Folksonomy engine #5219 when ready

Part of

• Make the edit mode of the mobile app compatible with OxF #4540