Move lsp config to local file structure

.config/nvim/lsp/air.lua

@@ -0,0 +1,14 @@
+---@brief
+---
+--- https://github.com/posit-dev/air
+---
+--- Air is an R formatter and language server, written in Rust.
+---
+--- Refer to the [documentation](https://posit-dev.github.io/air/editors.html) for more details.
+
+---@type vim.lsp.Config
+return {
+  cmd = { 'air', 'language-server' },
+  filetypes = { 'r' },
+  root_markers = { 'air.toml', '.air.toml', '.git' },
+}