[FR] Allow to use a specific font family for icons

I'm using `JetBrains Mono` as my terminal font and also have `Nerd Font Symbols` on my system. This is [the recommended way according to Kitty terminal maintainer](https://sw.kovidgoyal.net/kitty/faq/#kitty-is-not-able-to-use-my-favorite-font), and we can use a specific font family for symbols in kitty config file.

Since we cannot do the same with LazyGit, the icons aren't picked from `Nerd Font Symbols` and are most likely coming from my terminal font:


It would be nice if we could explicitly set a specific font family for the icons in LazyGit config file so that they're rendered properly in this case. I know I could just use a patched nerd font which includes symbols but I don't want to.