Assigning Empty Table (={}) does not unset the highlight groups

[ful1e5]

This isn't working in the newer codebase.

require('github-theme').setup({
  groups = {
    all = {
      -- this will remove the highlight groups
      ['@punctuation.bracket'] = {},
    },
  },
})

vim.cmd.colorscheme('github_dark')

Originally posted by @tmillr in #226 (comment)