message: feat: check pyright-langserver exist
diff: import { commands, ExtensionContext, LanguageClient, LanguageClientOptions, NodeModule, services, TransportKind, workspace } from 'coc.nvim';
  import { TextEdit, WorkspaceEdit } from 'vscode-languageserver-protocol';
  import { ProgressReporting } from './progress';
  +import { existsSync } from 'fs';
  export async function activate(context: ExtensionContext): Promise<void> {
  + const module = context.asAbsolutePath('node_modules/pyright/langserver.index.js');
  + if (!existsSync(module)) {
  + workspace.showMessage(`Pyright file doesn't exist, please reinstall coc-pyright`, 'error');
  + return;
  + }
  +
  const serverOptions: NodeModule = {
  - module: context.asAbsolutePath('node_modules/pyright/langserver.index.js'),
  + module,
  transport: TransportKind.ipc,
  };
  