Add disclaimer for theme appearance to match project README

Author: mcornella

Themes.md

@@ -10,6 +10,16 @@ If you do not want any theme enabled, just set `ZSH_THEME` to blank: `ZSH_THEME=
 
 Here is a collection of screenshots and descriptions of themes that have been contributed to Oh My Zsh. There are some missing from this page. If you want to add or edit descriptions, see the [format description](#theme-description-format) at the bottom of this page.
 
+> [!NOTE]
+> You will many times see screenshots for a zsh theme, and try it out, and find that it doesn't look the same for you.
+> 
+> This is because many themes require installing a [Powerline Font](https://github.com/powerline/fonts) or a [Nerd Font](https://github.com/ryanoasis/nerd-fonts) in order to render properly.
+> Without them, these themes will render weird prompt symbols. Check out [the FAQ](https://github.com/ohmyzsh/ohmyzsh/wiki/FAQ#i-have-a-weird-character-in-my-prompt) for more information.
+>
+> Also, beware that themes only control what your prompt looks like. This is, the text you see before or after your cursor, where you'll type your commands.
+> Themes don't control things such as the colors of your terminal window (known as _color scheme_) or the font of your terminal. These are settings that you can change in your terminal emulator.
+> For more information, see [what is a zsh theme](https://github.com/ohmyzsh/ohmyzsh/wiki/FAQ#what-is-a-zsh-theme).
+
 ## Themes
 
 ### robbyrussell