Add metadata to images

Several types of images are present on snoBoard:

• Logo & favicon
• Images in help
• Custom icons
• 2D structure (in target view & exported images)
• Generated interaction visualisation

Some metadata would need to be added to it:

• License
• Author (snoBoard)

A watermark (e.g. the snoBoard logo or favicon) could also be applied on some images (actually really good idea ? 🤷🏼)