Move lsp config to local file structure

.config/nvim/lsp/dhall_lsp_server.lua

@@ -0,0 +1,18 @@
+---@brief
+---
+--- https://github.com/dhall-lang/dhall-haskell/tree/master/dhall-lsp-server
+---
+--- language server for dhall
+---
+--- `dhall-lsp-server` can be installed via cabal:
+--- ```sh
+--- cabal install dhall-lsp-server
+--- ```
+--- prebuilt binaries can be found [here](https://github.com/dhall-lang/dhall-haskell/releases).
+
+---@type vim.lsp.Config
+return {
+  cmd = { 'dhall-lsp-server' },
+  filetypes = { 'dhall' },
+  root_markers = { '.git' },
+}