feat(plugin-lighthouse): export default Chrome flags

[hanna-skryl]

Closes #764

This pull request introduces DEFAULT_CHROME_FLAGS to @code-pushup/lighthouse-plugin, combining Chrome's default flags provided by chrome-launcher with --headless for streamlined headless execution.

The README has been updated to reflect this change.

[github-actions]

Code PushUp

🤨 Code PushUp report has both improvements and regressions – compared target commit b0de9ad with source commit 149f54b.

🕵️ See full comparison in Code PushUp portal 🔍

🏷️ Categories

🏷️ Category	⭐ Previous score	⭐ Current score	🔄 Score change
Security	🟡 87	🟡 82
Performance	🔴 48	🟡 52
Code coverage	🟢 90	🟢 90
Custom checks	🟡 67	🟡 67	–
Updates	🟡 78	🟡 78	–
Accessibility	🟢 91	🟢 91	–
Best Practices	🟢 100	🟢 100	–
SEO	🟡 61	🟡 61	–
Bug prevention	🟢 100	🟢 100	–
Code style	🟢 99	🟢 99	–

👍 1 group improved, 👎 2 groups regressed, 👍 5 audits improved, 👎 2 audits regressed, 12 audits changed without impacting score

🗃️ Groups

🔌 Plugin	🗃️ Group	⭐ Previous score	⭐ Current score	🔄 Score change
JS Packages	NPM audit	🟡 87	🟡 82
Lighthouse	Performance	🔴 48	🟡 52
Code coverage	Code coverage metrics	🟢 90	🟢 90

17 other groups are unchanged.

🛡️ Audits

🔌 Plugin	🛡️ Audit	📏 Previous value	📏 Current value	🔄 Value change
Lighthouse	Speed Index	🟥 7.6 s	🟥 6.2 s
Lighthouse	Largest Contentful Paint	🟨 3.6 s	🟨 3.3 s
JS Packages	Vulnerabilities for NPM prod dependencies.	🟩 0 vulnerabilities	🟩 3 vulnerabilities (3 low)
Lighthouse	First Meaningful Paint	🟨 3.2 s	🟨 3.0 s
Lighthouse	First Contentful Paint	🟥 3.1 s	🟨 3.0 s
Lighthouse	Time to Interactive	🟥 17.6 s	🟥 16.0 s
Code coverage	Line coverage	🟩 91.5 %	🟩 91.5 %
Lighthouse	Minimizes main-thread work	🟥 25.0 s	🟥 20.1 s
Lighthouse	Total Blocking Time	🟥 9,830 ms	🟥 5,940 ms
Lighthouse	JavaScript execution time	🟥 11.3 s	🟥 9.2 s
Lighthouse	Metrics	🟩 100%	🟩 100%
Lighthouse	Avoids enormous network payloads	🟩 Total size was 1,819 KiB	🟩 Total size was 1,821 KiB
Lighthouse	Max Potential First Input Delay	🟥 3,870 ms	🟥 2,850 ms
Lighthouse	Uses efficient cache policy on static assets	🟨 27 resources found	🟨 27 resources found
Lighthouse	Eliminate render-blocking resources	🟥 Potential savings of 370 ms	🟥 Potential savings of 520 ms
Lighthouse	Server Backend Latencies	🟩 270 ms	🟩 130 ms
Lighthouse	Initial server response time was short	🟩 Root document took 400 ms	🟩 Root document took 490 ms
Lighthouse	Network Round Trip Times	🟩 70 ms	🟩 50 ms
Lighthouse	Avoids an excessive DOM size	🟥 2,237 elements	🟥 2,236 elements

494 other audits are unchanged.

[matejchalk]

Nice improvement 👍