[mini.base16]: add customization for bold and italic.

[mubin-thinks]

Hello @echasnovski, as far as I know currently mini.base16 doesn't support enabling italic/bold for different bases. It limits the ability to customize for color-scheme makers and users. It would be helpful to have such feature.

Thanks.

[echasnovski]

Thanks for the suggestion!

'mini.base16' follows the Base16 color scheme system with reference implementation being chriskempson/base16-vim. So enabling any extra styling for bases is out of scope.

The suggested solution here is to manually override highlight groups that need tweaking with vim.api.nvim_set_hl() or vim.cmd.highlight().