feat(nvim): add null-ls for markdown formatting

home-manager/neovim/default.nix

@@ -69,6 +69,7 @@
         lsp-status-nvim
         rust-tools-nvim
         lua-dev-nvim
+        null-ls-nvim
       ];
 
       extraConfig = ''

home-manager/neovim/lspconfig.lua

@@ -93,3 +93,15 @@ local luadev = require("lua-dev").setup({
 })
 
 lspconfig["sumneko_lua"].setup(luadev)
+
+-- setup null-ls for markdown formatting
+local null_ls = require("null-ls")
+null_ls.setup({
+    sources = {
+        null_ls.builtins.formatting.prettier.with({
+            filetypes = { "markdown" }
+        }),
+    },
+
+    on_attach = on_attach,
+})