Closes #146: Adds headless config

[Miraeld]

Description

Fixes #146
This PR makes the end-to-end (e2e) tests compatible with headless mode, allowing them to be run within a Docker container. This ensures a consistent testing environment for all team members, regardless of their local setup.

Type of change

• Enhancement (non-breaking change which improves an existing functionality).

Detailed scenario

To trigger the new code, set the ENV_HEADLESS environment variable to 'true' when running the e2e tests. This will launch the Chromium browser in headless mode.

Technical description

Documentation

The changes in this PR involve adding a new ENV_HEADLESS environment variable and updating the Chromium launch configuration to use this variable. If ENV_HEADLESS is 'true', the Chromium browser is launched in headless mode. This is often used in automated testing environments.

Don't forget to modify you config file

New dependencies

No new dependencies are required for this change.

Risks

There are no known performance or security risks associated with this change.

Mandatory Checklist

Code validation

• I validated all the Acceptance Criteria. If possible, provide screenshots or videos.
• I triggered all changed lines of code at least once without new errors/warnings/notices.
• I implemented built-in tests to cover the new/changed code.

Code style

• I wrote a self-explanatory code about what it does.
• I protected entry points against unexpected inputs.
• I did not introduce unnecessary complexity.
• Output messages (errors, notices, logs) are explicit enough for users to understand the issue and are actionnable.

Additional Checks

• In the case of complex code, I wrote comments to explain it.
• When possible, I prepared ways to observe the implemented system (logs, data, etc.).
• I added error handling logic when using functions that could throw errors (HTTP/API request, filesystem, etc.)