fix: consider attaching when editing new file

BufReadPost does not trigger when editing a nonexistent file, so
language servers would not automatically attach when editing a new file
if autostart was disabled or if the server had no associated filetypes.
This fixes that by adding BufNewFile to autocommands hooked to
BufReadPost.

lua/lspconfig/configs.lua

@@ -100,7 +100,7 @@ function configs.__newindex(t, config_name, config_def)
 
     if config.autostart == true then
       local event_conf = config.filetypes and { event = 'FileType', pattern = config.filetypes }
-        or { event = 'BufReadPost' }
+        or { event = { 'BufReadPost', 'BufNewFile' } }
       api.nvim_create_autocmd(event_conf.event, {
         pattern = event_conf.pattern or '*',
         callback = function(opt)
@@ -136,7 +136,7 @@ function configs.__newindex(t, config_name, config_def)
         end
 
         if root_dir then
-          api.nvim_create_autocmd('BufReadPost', {
+          api.nvim_create_autocmd({ 'BufReadPost', 'BufNewFile' }, {
             pattern = fn.fnameescape(root_dir) .. '/*',
             callback = function(arg)
               M.manager.try_add_wrapper(arg.buf, root_dir)