Clean up README badges and add CircleCI config

.circleci/config.yml

@@ -0,0 +1,26 @@
+version: 2.1
+jobs:
+  test-java:
+    docker:
+      - image: cimg/openjdk:25.0
+    steps:
+      - checkout
+      - run:
+          name: Calculate cache key
+          command: |-
+            find . -name 'pom.xml' -o -name 'gradlew*' -o -name '*.gradle*' | \
+                    sort | xargs cat > /tmp/CIRCLECI_CACHE_KEY
+      - restore_cache:
+          key: cache-{{ checksum "/tmp/CIRCLECI_CACHE_KEY" }}
+      - run:
+          command: mvn verify
+      - store_test_results:
+          path: target/surefire-reports
+      - save_cache:
+          key: cache-{{ checksum "/tmp/CIRCLECI_CACHE_KEY" }}
+          paths:
+            - ~/.m2/repository
+workflows:
+  build-and-test:
+    jobs:
+      - test-java

README.md

@@ -1,7 +1,8 @@
-[![maven build](https://github.com/lpenap/java-patterns-and-constructs/actions/workflows/merged_master.yml/badge.svg)](https://github.com/lpenap/java-patterns-and-constructs/actions/workflows/merged_master.yml)
+[![CircleCI](https://dl.circleci.com/status-badge/img/gh/lpenap/java-patterns-and-constructs/tree/master.svg?style=shield)](https://dl.circleci.com/status-badge/redirect/gh/lpenap/java-patterns-and-constructs/tree/master)
+[![Build](https://github.com/lpenap/java-patterns-and-constructs/actions/workflows/merged_master.yml/badge.svg)](https://github.com/lpenap/java-patterns-and-constructs/actions/workflows/merged_master.yml)
 [![GitHub release](https://img.shields.io/github/release/lpenap/java-patterns-and-constructs)](//github.com/lpenap/java-patterns-and-constructs/releases/latest)
-[![codebeat badge](https://codebeat.co/badges/4c328c5d-1722-459f-aaa1-437a0ed6201f)](https://codebeat.co/projects/github-com-lpenap-java-patterns-and-constructs-master)
 ![Coverage](.github/badges/jacoco.svg)
+![Branches](.github/badges/branches.svg)
 
 # Java Design Patterns and Constructs
 Collection of patterns and other constructs in Java for educational purposes. (See *Contributing* section if you would like to contribute).