Update: 21-09-16

Spoiler Bot (beta)

@spoilingbot

Send spoilers discreetly, so no one hates you for doing it.
This is an inline bot, so you don't have to add it anywhere. You just need to type @SpoilingBot in any conversation, followed by the spoiler you want to hide, and WITHOUT hitting the send button, tap the first option in the popup menu.