Express template updates

Changes:

• Updated node to the latest stable version
• Added tests
• Applied the example to be consistent with industry practices (mocha/supertest)
• Removed pug files as today express is mostly used for creating APIs while react/svelte/vue/angular is used on the frontend
• Added .docker-ignore to avoid copying the node_modules into the docker container
• Simplified the example, allowing for easier adoption
• Simplified the dockerfile
• Updated the links in the README.md file
• Removed jenkinsfile as it's not really needed 😄