Add docker for production

[arthurpar06]

We will be using https://serversideup.net/open-source/docker-php/

Closes #1815

What’s left to do:

• Create a custom image with the extensions we need, Composer, and (maybe) mariadb-client
• Add an "installation" script to run "composer dump-autoload" on the first launch
• Remove sample module
• Create a .env.example file
• Update installer to support step3 only install
• Build custom image in CI (will be done in another PR)
• Update docs (will be done in another PR)
• Perform real-world testing

[gitguardian]

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🔎 Detected hardcoded secret in your pull request

GitGuardian id	GitGuardian status	Secret	Commit	Filename
2856813	Triggered	Generic Password	01b1a83	.env.example	View secret

🛠 Guidelines to remediate hardcoded secrets

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