Move lsp config to local file structure

.config/nvim/lsp/ccls.lua

@@ -0,0 +1,53 @@
+---@brief
+---
+--- https://github.com/MaskRay/ccls/wiki
+---
+--- ccls relies on a [JSON compilation database](https://clang.llvm.org/docs/JSONCompilationDatabase.html) specified
+--- as compile_commands.json or, for simpler projects, a .ccls.
+--- For details on how to automatically generate one using CMake look [here](https://cmake.org/cmake/help/latest/variable/CMAKE_EXPORT_COMPILE_COMMANDS.html). Alternatively, you can use [Bear](https://github.com/rizsotto/Bear).
+---
+--- Customization options are passed to ccls at initialization time via init_options, a list of available options can be found [here](https://github.com/MaskRay/ccls/wiki/Customization#initialization-options). For example:
+---
+--- ```lua
+--- vim.lsp.config("ccls", {
+---   init_options = {
+---     compilationDatabaseDirectory = "build";
+---     index = {
+---       threads = 0;
+---     };
+---     clang = {
+---       excludeArgs = { "-frounding-math"} ;
+---     };
+---   }
+--- })
+--- ```
+
+local function switch_source_header(client, bufnr)
+  local method_name = 'textDocument/switchSourceHeader'
+  local params = vim.lsp.util.make_text_document_params(bufnr)
+  client:request(method_name, params, function(err, result)
+    if err then
+      error(tostring(err))
+    end
+    if not result then
+      vim.notify('corresponding file cannot be determined')
+      return
+    end
+    vim.cmd.edit(vim.uri_to_fname(result))
+  end, bufnr)
+end
+
+---@type vim.lsp.Config
+return {
+  cmd = { 'ccls' },
+  filetypes = { 'c', 'cpp', 'objc', 'objcpp', 'cuda' },
+  root_markers = { 'compile_commands.json', '.ccls', '.git' },
+  offset_encoding = 'utf-32',
+  -- ccls does not support sending a null root directory
+  workspace_required = true,
+  on_attach = function(client, bufnr)
+    vim.api.nvim_buf_create_user_command(bufnr, 'LspCclsSwitchSourceHeader', function()
+      switch_source_header(client, bufnr)
+    end, { desc = 'Switch between source/header' })
+  end,
+}