Move lsp config to local file structure

.config/nvim/lsp/dockerls.lua

@@ -0,0 +1,30 @@
+---@brief
+---
+--- https://github.com/rcjsuen/dockerfile-language-server-nodejs
+---
+--- `docker-langserver` can be installed via `npm`:
+--- ```sh
+--- npm install -g dockerfile-language-server-nodejs
+--- ```
+---
+--- Additional configuration can be applied in the following way:
+--- ```lua
+--- vim.lsp.config('dockerls', {
+---     settings = {
+---         docker = {
+--- 	    languageserver = {
+--- 	        formatter = {
+--- 		    ignoreMultilineInstructions = true,
+--- 		},
+--- 	    },
+--- 	}
+---     }
+--- })
+--- ```
+
+---@type vim.lsp.Config
+return {
+  cmd = { 'docker-langserver', '--stdio' },
+  filetypes = { 'dockerfile' },
+  root_markers = { 'Dockerfile' },
+}