#1806 Add DevContainer configuration

[MarianPalkus]

Description

Add DevContainers based on quickstart-project to improve the handling of the development environment. Ports 80 (quickstart project) and 8025 (mailhog) are forwarded within the DevContainer setup.

Addressing #1806.

Implementation

• add devcontainer.json based on docker compose
• add a docker-compose file for devcontainer setup
• there were issues to make mailslurper accessible through codespace port forwarding therefore it has been replaced by mailhog

Tests

The setup can be tried here:

• https://github.com/MarianPalkus/hanko
• "Code" -> "Codespaces ..." -> "New with options..."
• 
• Select branch "devcontainers" and "create codespace"
• 
• the codespace should be opened
• After initialization has finished (might take some minutes) the quickstart-page can be accessed via "Ports" -> Port 80 -> "Open in Browser"
• 
• mailhog can be accessed via "Ports" -> Port 8025 -> "Open in Browser"

The quickstart-example should be fully working:

Todos

• the service entry in the devcontainer docker-compose file might not be required
• code changes should directly be visible in the quickstart-page: configure hmr/fast refresh for elements and frontend-sdk and watch-build for backend
• devcontainer-docker-compose-file and custom config files might be moved to the .devcontainers directory
• webauthn origin config might be wrong

Additional context