National Poetry Month 2021 Billy throwback

[dukealien]

Can someone tell me where to find code for creating the "Spoiler" button?  I checked the "How to Use" section.  I see something about it from Billy but don't understand the instructions.

At the beginning of the text you want to conceal put (open square bracket)spoiler(close square bracket).  At the end of the text put (bra)/spoiler(ket).  Like this (see the codes in the edit frame):

here's the spoiled, er, spoiler text