Adding an option to set default text color

**Is your feature request related to a problem? Please describe.**
I am always frustrated when I open lazygit in alacritty and gocui picks the wrong default text-color(some dark color eventhough my text color is completly different tried different colorschemes, however it simply ignores them and picks the same dark color) and then having to work with no contrast in lazygit. Also see #1565

**Describe the solution you'd like**
I would like that the code is changed such that there is an option for the default text color which can be changed in the config.yml
I think the changes need to made here:
https://github.com/jesseduffield/lazygit/blob/2696a63a0a8491b6bb0ebd3350522f4b8198f14f/pkg/config/user_config.go#L47
and here
https://github.com/jesseduffield/lazygit/blob/2696a63a0a8491b6bb0ebd3350522f4b8198f14f/pkg/theme/theme.go#L45

**Describe alternatives you've considered**
I file a bug report with gocui but I have no experience with go.

**Additional context**
Add any other context or screenshots about the feature request here.