CI/CD and other maintance improvements

Configure CI/CD with following steps:
- On PR: Validate lint & prettier
- On push to master:
  - Publish "dev" version
  - Run integration tests, to confirm "dev" version works ok
  - If version was bumped in serverless.component.yml issue a release tag
- On release tag: Publish new version
Upgrade lint & prettier configuration to @serverless/eslint-config
Ensure to install all nested packages on npm install
Commit in src/package-lock.json to ensure reproducible component (at given version) installs
Cleanup package.json from npm registry related information (as it's not intended to be published to npm)
Move tests to test folder, as it's more common name by general conventions
Cleanup .gitignore (https://gist.github.com/subfuzion/db7f57fff2fb6998a16c)
Introduce .editorconfig

serverless-components / express