feat(slack-app): custom resource to deploy Slack apps (#136)

Custom resource to deploy Slack apps from manifests

See https://api.slack.com/reference/manifests

Author: jogold

.gitattributes

@@ -7,7 +7,6 @@ const project = new awscdk.AwsCdkConstructLibrary({
   cdkVersion: '2.1.0',
   name: 'cloudstructs',
   repository: 'https://github.com/jogold/cloudstructs.git',
-  workflowNodeVersion: '14.17.0',
   peerDeps: [
     '@aws-cdk/aws-apigatewayv2-alpha',
     '@aws-cdk/aws-apigatewayv2-integrations-alpha',
@@ -19,6 +18,7 @@ const project = new awscdk.AwsCdkConstructLibrary({
   devDeps: [
     '@types/aws-lambda',
     '@types/tsscmp',
+    'aws-cdk',
     'aws-sdk',
     'aws-sdk-mock',
     'esbuild',