docs/missing code-actions config in the docs

[stefano-regosa-deel]

As the title it seems like are missing in the DOC information about how to setup code-actions !

I'm willing to open a PR to add this if needed !

local code_actions = require "lvim.lsp.null-ls.code_actions"
code_actions.setup {
  { 
    exe = "eslint_d",
    filetypes = { "typescript", "typescriptreact", "javascript", "javascriptreact", "react" },
  },
}