fix(node-resolve): fs.exists is incorrectly promisified (#835)

Co-authored-by: Liam McLoughlin <lmcloughlin@google.com>

packages/node-resolve/src/fs.js

@@ -2,8 +2,16 @@ import fs from 'fs';
 
 import { promisify } from 'util';
 
-export const exists = promisify(fs.exists);
+export const access = promisify(fs.access);
 export const readFile = promisify(fs.readFile);
 export const realpath = promisify(fs.realpath);
 export { realpathSync } from 'fs';
 export const stat = promisify(fs.stat);
+export async function exists(filePath) {
+  try {
+    await access(filePath);
+    return true;
+  } catch {
+    return false;
+  }
+}