Tag Cog: Support wrapping tag message in a spoiler

[Exper1mental]

When a tag is invoked within a spoiler, e.g. || Falcon and Winter Solder spoilers: $spoiler ||, I suggest ClemBot post that tag wrapped in a spoiler so images/previews don't ruin the surprise for those who don't want to know.

[Jay-Madden]

This is an interesting idea, implementation could be a bit tricky tho