Support GitLab CI/CD custom collapsible sections

[sanmai-NL]

Is your feature request related to a problem? Please describe.
MegaLinter can generate a lot of output. Collapsible section help structure this.

Describe the solution you'd like
Use GitLab CI/CD's custom collapsible sections.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[nvuillam]

@sanmai-NL I tried that a million years ago but didn't succeed :/

If you share a raw log file that works with collapsible sections, I can try again :)

[github-actions]

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