Add Reporter

Guide through adding a new reporter named $ARGUMENTS to MegaLinter.

Steps:

1. Create the class in megalinter/reporters/<Name>Reporter.py extending megalinter.Reporter
2. Implement required methods:
   • manage_activation() — check env var like <NAME>_REPORTER=true to enable/disable
   • produce_report() — generate the report output
   • Optionally: initialize(), add_report_item()
3. Register the reporter — check how existing reporters are discovered and loaded in megalinter/MegaLinter.py
4. Reference patterns from existing reporters:
   • Simple output: ConsoleReporter.py, TapReporter.py
   • CI integration: GithubCommentReporter.py, GitlabCommentReporter.py
   • File output: JsonReporter.py, SarifReporter.py
   • External service: ApiReporter.py, EmailReporter.py
5. Update documentation — add a docs page describing configuration
6. Update CHANGELOG.md in the repository root (not docs/) — add one line under Reporters in the beta section:

   - Add <ReporterName>: <what CI system or output format it supports, one sentence>
   

7. Branch naming: use user/add-<reporter-name>-reporter