feat: Add support for rcarriga/nvim-dap-ui

[fnune]

This PR adds support for nvim-dap-ui. I also saw that a DiagnosticOk highlight was missing, so I added it (I was initially using it for the DAP highlights).

Before (dark)	Before (light)	After (dark)	After (light)

If anyone's curious how to add the play, stop, etc. icons, here't my (partial) config (requires nvim-web-devicons):

  {
    "rcarriga/nvim-dap-ui",
    lazy = true,
    dependencies = { "mfussenegger/nvim-dap" },
    opts = {
      controls = {
        element = "repl",
        enabled = true,
        icons = {
          disconnect = " F1",
          play = " F5",
          pause = " F6",
          terminate = " F7",
          run_last = " F4",
          step_back = " F9",
          step_over = " F10",
          step_into = " F11",
          step_out = " F12",
        },
      },
    }
  }