Update .gitlab-ci.yml

.gitlab-ci.yml

+default:
+  image:  maven:3-jdk-11
+
+
+stages:
+  - install
+  - build
+
+maven-job:
+  stage: install
+  script:
+    - mvn clean package
+    - mvn package
+
+
+docker-build-job:
+  stage: build
+  image: docker:latest
+  needs:
+    - "maven-job"
+  script:
+    - docker build -t nisum-cicd-task:latest
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