OT: Feature Request - Spoiler Tags

I was reading The Acolyte thread, and came across this comment, containing the following text:

My wife was also really excited about that too and then they SPOILER ALERT so soon.

How difficult would it be to implement a spoiler tag fuctionality similar to reddit? Maybe an additional box similar to the bold/italics/underline/strikethrough functionality, that creates spoiler tags, such that any text between them is blacked out until you click the blacked out area, upon which the spoiler text appears? That would allow people to read a spoiler thread and get some information about a show without getting real spoilers.

Is this something that we can volunteer some programming time to implement for you? I'd love to help (though I'm sure it would take me longer than somebody more proficient in whatever programming language the board is built).

And now that I mention the blacked out area, is a dark mode possible for the site, or would that take a ridiculous amount of time to implement? I tried setting dark mode in Chrome, but it only affects the chrome part of the browser, not the site part.

(Wasn't sure if I should've put this on the TKP forum or OT.)