feat(nvim/bufferline): use lazyvim style and icons

pkgs/nvim/config/bufferlines/bufferline.nix

@@ -1,8 +1,22 @@
 {
+  helpers,
+  icons,
+  ...
+}: {
   plugins = {
     bufferline = {
       enable = true;
-      separatorStyle = "thick"; # “slant”, “padded_slant”, “slope”, “padded_slope”, “thick”, “thin”
+      separatorStyle = "thin"; # “slant”, “padded_slant”, “slope”, “padded_slope”, “thick”, “thin”
+      alwaysShowBufferline = false;
+      diagnostics = "nvim_lsp";
+      diagnosticsIndicator = ''
+        function(_, _, diag)
+          local icons = ${helpers.toLuaObject icons.diagnostics}
+          local ret = (diag.error and icons.Error .. diag.error .. " " or "")
+            .. (diag.warning and icons.Warn .. diag.warning or "")
+          return vim.trim(ret)
+        end
+      '';
       offsets = [
         {
           filetype = "neo-tree";