feat: add healthcheck

[pichoemr]

https://github.com/lenra-io/lenra_cli/issues/47

Checklist

• [x] I didn't over-scope my PR
• [x] My PR title matches the commit convention
• [x] I did not include breaking changes
• [ ] I included unit tests that cover my changes
• [ ] I added/updated the documentation about my changes
• [x] I made my own code-review before requesting one

Description of the changes

Add a health check plug that handles the /healtcheck request, responds 200 status and halt the connection.

[shiipou]

:tada: This PR is included in version 1.0.0-alpha.1 :tada:

The release is available on:

• GitHub release
• v1.0.0-alpha.1

Your semantic-release bot :package::rocket: