Move lsp config to local file structure

.config/nvim/lsp/rls.lua

@@ -0,0 +1,35 @@
+---@brief
+---
+--- https://github.com/rust-lang/rls
+---
+--- rls, a language server for Rust
+---
+--- See https://github.com/rust-lang/rls#setup to setup rls itself.
+--- See https://github.com/rust-lang/rls#configuration for rls-specific settings.
+--- All settings listed on the rls configuration section of the readme
+--- must be set under settings.rust as follows:
+---
+--- ```lua
+--- vim.lsp.config('rls', {
+---   settings = {
+---     rust = {
+---       unstable_features = true,
+---       build_on_save = false,
+---       all_features = true,
+---     },
+---   },
+--- })
+--- ```
+---
+--- If you want to use rls for a particular build, eg nightly, set cmd as follows:
+---
+--- ```lua
+--- cmd = {"rustup", "run", "nightly", "rls"}
+--- ```
+
+---@type vim.lsp.Config
+return {
+  cmd = { 'rls' },
+  filetypes = { 'rust' },
+  root_markers = { 'Cargo.toml' },
+}