How to make “spoiler” text in github wiki pages?

GFM supports a subset of HTML. For now, you can wrap your question in a <summary> and your answer in any standard HTML tag like <p> and wrap the whole thing in the <details> tag.

So if you do this

<details> 
  <summary>Q1: What is the best Language in the World? </summary>
   A1: JavaScript 
</details>

You get this -> https://github.com/gaurav21r/Spoon-Knife/wiki/Read-More-Test

Browser support is an Issue.

The thing with GitHUB wiki is that it allows you write text in other formats like AsciiDoc, RST etc. Probabaly there’s solution in those too. These are 2 formats that are far more feature rich than Markdown.