chore: add CircleCI integration

.circleci/config.yml

@@ -0,0 +1,18 @@
+version: 2
+jobs:
+  build:
+    docker:
+      - image: hashicorp/terraform:light
+    working_directory: ~/repo/examples/root-example
+    steps:
+      - checkout:
+          path: ~/repo
+      - run:
+          name: Initialize a root module.
+          command: terraform init
+      - run:
+          name: Make sure the syntax is correct.
+          command: terraform validate -var access_key=DUMMY -var secret_key=DUMMY
+      - run:
+          name: Make sure format wouldn't produce any diffs.
+          command: terraform fmt -check=true

README.md

@@ -1,5 +1,7 @@
 # terraform-aws-secure-baseline
 
+[![CircleCI](https://circleci.com/gh/nozaq/terraform-aws-secure-baseline.svg?style=svg)](https://circleci.com/gh/nozaq/terraform-aws-secure-baseline)
+
 [Terraform Module Registry](https://registry.terraform.io/modules/nozaq/secure-baseline/aws)
 
 A terraform module to set up your AWS account with the reasonably secure configuration baseline.