fix: expose utility functions in nohighlight entrypoint (#698)

Author: Stopa

core/src/index.nohighlight.tsx

@@ -3,13 +3,16 @@ import * as commands from './commands/';
 import * as MarkdownUtil from './utils/markdownUtils';
 import './index.less';
 
+export { headingExecute } from './commands/title';
 export * from './commands/';
 export * from './commands/group';
 export * from './utils/markdownUtils';
 export * from './utils/InsertTextAtPosition';
 export * from './Editor.nohighlight';
 export * from './Context';
 export * from './Types';
+export { default as handleKeyDown } from './components/TextArea/handleKeyDown';
+export { default as shortcuts } from './components/TextArea/shortcuts';
 
 export { MarkdownUtil, commands };