nvim: lua: lsp: Add support for incremental sync

Support for incremental sync landed in neovim with this MR.
https://github.com/neovim/neovim/pull/13371

nvim/.config/nvim/lua/lsp.lua

@@ -49,6 +49,10 @@ local on_attach = function(client, bufnr)
   completion.on_attach(client, bufnr)
   lsp_status.on_attach(client, bufnr)
 
+  if client.config.flags then
+    client.config.flags.allow_incremental_sync = true
+  end
+
   local opts = { noremap=true, silent=true }
   vim.api.nvim_buf_set_keymap(bufnr, 'n', 'gd', '<cmd>lua vim.lsp.buf.definition()<CR>', opts)
   vim.api.nvim_buf_set_keymap(bufnr, 'n', 'K',  '<cmd>lua vim.lsp.buf.hover()<CR>', opts)