RbxThumb format support for developer product icons

As a Roblox developer, it is currently impossible to use the brand new ContentId format RbxThumb to load developer product icons.

Being able to load developer product icons would be quite useful for many developers! The largest use case would be in-game shops that use developer products to prompt purchases for goods such as boosts or currency. Format support for developer icons would remove the need to upload images when making a new product or changing an existing product’s icon.