Update theme to support `<details>` element

[thanhnguyen2187]

This HTML block

<details>
  <summary>Hello</summary>
  World
</details>

Looks normal in light theme

But the text won't change its color in dark theme (I had to select it to make it readable)

Is there anyway to fix this? Thanks!

[dullage]

Hey @thanhnguyen2187. This custom HTML isn't something supported by the current theme, but I'll tag this as a suggestion for consideration.