docs: add readme to vtl resolvers directory

packages/amplify-category-api/resources/awscloudformation/resolver-readme/README.md

@@ -0,0 +1,2 @@
+Any resolvers that you add in this directory will override the ones automatically generated by Amplify CLI and will be directly copied to the cloud. 
+For more information, visit [https://docs.amplify.aws/cli/graphql-transformer/resolvers](https://docs.amplify.aws/cli/graphql-transformer/resolvers)

packages/amplify-category-api/src/__tests__/provider-utils/awscloudformation/cfn-api-artifact-handler.test.ts

@@ -105,8 +105,8 @@ describe('create artifacts', () => {
 
   it('writes the default custom resources stack', async () => {
     await cfnApiArtifactHandler.createArtifacts(addRequestStub);
-    expect(fs_mock.copyFileSync.mock.calls.length).toBe(1);
-    expect(fs_mock.copyFileSync.mock.calls[0]).toEqual([
+    expect(fs_mock.copyFileSync.mock.calls.length).toBe(2);
+    expect(fs_mock.copyFileSync.mock.calls[1]).toEqual([
       path.join(rootAssetDir, 'cloudformation-templates', 'defaultCustomResources.json'),
       path.join(backendDirPathStub, category, addRequestStub.serviceConfiguration.apiName, 'stacks', 'CustomResources.json'),
     ]);

packages/amplify-category-api/src/provider-utils/awscloudformation/cfn-api-artifact-handler.ts

@@ -59,6 +59,7 @@ class CfnApiArtifactHandler implements ApiArtifactHandler {
     const stacksDirectoryPath = path.join(resourceDir, stacksDirName);
     if (!fs.existsSync(stacksDirectoryPath)) {
       fs.mkdirSync(stacksDirectoryPath);
+      fs.copyFileSync(path.join(rootAssetDir, 'resolver-readme', 'README.md'), `${resolverDirectoryPath}/README.md`);
     }
 
     // During API add, make sure we're creating a transform.conf.json file with the latest version the CLI supports.