Including the time when the NFT was generated in the SVG

[PaulRBerg]

As recommended by Cantina here.

My thoughts:

• Not sure where we could include this property - we may have to replace a part of the current design (ref: Walkthrough: NFT panoply (review grid) #520)
• A major difficulty would be having to clarify that this property stands for the time when the NFT was generated, and not to any intrinsic property of the stream itself (e.g., the time when the stream was created)
• Including a raw Unix timestamp in the SVG would be (mostly) useless; to do it properly, we would need to turn the block.timestamp into a human-readable date using a library like Solady's DateTimeLib). Implementing this is non-trivial.

Given the problems above, I remain unconvinced about the value of including the generated time in the NFT SVG. We may not implement this feature any time soon, but I opened this issue to shine some light on the underlying issue and open up the conversation in case anyone comes up with a creative workaround.

[PaulRBerg]

Going to close this because:

1. Users requested other updates to the NFT SVG, e.g. Add total amount in NFT descriptor cards #638
2. In the grand scheme of things, it is a minor issue