Replace h2-proxy by Vulcain

Preserve DX, as user is likely to just enter "localhost" in the browser's address bar

Add mercure.jwtKey

Bump deps

I got an `Unauthorized error` and figured out I didn't set the Mercure JWT key. I propose to add the key to `values.yaml` so it will be less easy to miss.

Bump APCu to 5.1.18

fixed broken link for LICENSE file

Co-Authored-By: Antoine Bluchet <soyuka@users.noreply.github.com>

* Added license badge and missing punctuation

* Added link for Swagger

* Removed license badge

Feat: remove coc file

Switch to the official varnish Docker image

Update CONTRIBUTING.md

Instead of using git submodule add

* deps(react): update react scripts to latest version

* update dependencies in yarn lock

Split reference Docker Compose production setup into separate repository

HAL stateless.co domain is suspended. Changed HAL url to their GitHub.

Update CONTRIBUTING.md to reflect pull request template

Make hyperlink more readable in Code of Conduct

Disable OPCache timestamps check in prod

Also fix problem with TRUSTED_HOSTS regex

Helm: Error if --set varnish.enabled=false - Logical error

Expose Mercure through the TLS proxy

Use PHPUnit 8 by default

Add a reference Docker Compose setup for production