fix: log variable substitution, CSRF exclusions, and README overhaul

[audunru]

Summary

• Use PHP string interpolation in LogCspViolation and LogReport log messages (fixes variable not being substituted in log output)
• Exclude all CSRF middleware variants from the reports route (not just the default one)
• Restructure README: add GitHub Actions + Coveralls badges, replace separate "Listening for events" / "Built-in listeners" sections with a single "Getting started" section using Event::listen() in AppServiceProvider::boot(), move DTO/event reference tables to a new "Reference" section

Closes #4

Test plan

• Existing test suite passes (composer test)
• Log output for CSP violations and generic reports contains the expected interpolated values
• README renders correctly on GitHub

🤖 Generated with Claude Code

[audunru]

🎉 This PR is included in version 2.0.0 🎉

The release is available on GitHub release

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