Move lsp config to local file structure

.config/nvim/lsp/ada_ls.lua

@@ -0,0 +1,31 @@
+---@brief
+---
+--- https://github.com/AdaCore/ada_language_server
+---
+--- Installation instructions can be found [here](https://github.com/AdaCore/ada_language_server#Install).
+---
+--- Workspace-specific [settings](https://github.com/AdaCore/ada_language_server/blob/master/doc/settings.md) such as `projectFile` can be provided in a `.als.json` file at the root of the workspace.
+--- Alternatively, configuration may be passed as a "settings" object to `vim.lsp.config('ada_ls', {})`:
+---
+--- ```lua
+--- vim.lsp.config('ada_ls', {
+---     settings = {
+---       ada = {
+---         projectFile = "project.gpr";
+---         scenarioVariables = { ... };
+---       }
+---     }
+--- })
+--- ```
+
+local util = require 'lspconfig.util'
+
+---@type vim.lsp.Config
+return {
+  cmd = { 'ada_language_server' },
+  filetypes = { 'ada' },
+  root_dir = function(bufnr, on_dir)
+    local fname = vim.api.nvim_buf_get_name(bufnr)
+    on_dir(util.root_pattern('Makefile', '.git', 'alire.toml', '*.gpr', '*.adc')(fname))
+  end,
+}