themes: add custom themes directory support to `lstheme` (#7236)
themes: add custom themes directory support to `lstheme` (#7236)

`lstheme` command used to list only the themes listed in `$ZSH/themes/` directory. This commit adds themes in `$ZSH_CUSTOM/themes/` also to the theme listings.
tekniklr/oh-my-zsh,tekniklr/oh-my-zsh