As a bootik owner, I want to be able to combine a product preview with a dedicated challenge gauge

[Tirodem]

This US need to be reforged, because we did a lot with widgets, and there's more than meet the eyes.

We need :

• a specific product widget template to display stock left for a product
• a specific product widget template to display progression of a chalenge linked to a product + a way on this widget to specify the challenge ID (in case of multiple challenge whitelisting the product)

High effort, low value & priority, it's going on the fridge for now.

[Tirodem]

Previous description :

Following #45 :

• add the option /product/{id}/widget?gauge=ZZZ
• when setted as widget option, display the gauge on the product widget
  
  Don't bother with the "Hurry up! Only 12 left" from design, only include the progression bar.

Integrations from preview options img = 2 & 3 :

Integrations from preview options img = 4 :