README: Add neovim instructions

Closes #214

README.md

@@ -80,6 +80,54 @@ treefmt-nix.mkWrapper nixpkgs {
 ```
 
 More information about configuration can be found in [the official README](https://github.com/numtide/treefmt-nix?tab=readme-ov-file#integration-into-nix).
+
+### neovim + nixd
+
+```lua
+local nvim_lsp = require("lspconfig")
+nvim_lsp.nixd.setup({
+ settings = {
+ nixd = {
+ formatting = {
+ command = { "nixfmt" },
+ },
+ },
+ },
+})
+```
+
+This only works when `nixfmt-rfc-style` is installed (see above for installation instructions).
+
+### neovim + nil
+
+```lua
+local nvim_lsp = require("lspconfig")
+nvim_lsp.nil_ls.setup({
+ settings = {
+ ['nil'] = {
+ formatting = {
+ command = { "nixfmt" },
+ },
+ },
+ },
+})
+```
+
+This only works when `nixfmt-rfc-style` is installed (see above for installation instructions).
+
+### neovim + none-ls
+
+```lua
+local null_ls = require("null-ls")
+null_ls.setup({
+ sources = {
+ null_ls.builtins.formatting.nixfmt,
+ },
+})
+```
+
+This only works when `nixfmt-rfc-style` is installed (see above for installation instructions).
+
 ## Development
 
 ### With Nix