fix(plugin-js-packages): add ignoreExitCode option for yarn v2 package manager

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Fix #877

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@matejchalk Did I miss something, or are there no e2e tests for the js-packages-plugin?
Where could I write a test to show that the fix is working?

[github-actions]

Code PushUp

🤨 Code PushUp report has both improvements and regressions – compared target commit 789e46a with source commit 1353b20.

🕵️ See full comparison in Code PushUp portal 🔍

🏷️ Categories

🏷️ Category	⭐ Previous score	⭐ Current score	🔄 Score change
Performance	🔴 48	🔴 48
Custom checks	🟡 67	🟡 67	–
Code coverage	🟡 90	🟡 90	–
Security	🟡 73	🟡 73	–
Updates	🟡 76	🟡 76	–
Accessibility	🟢 91	🟢 91	–
Best Practices	🟢 100	🟢 100	–
SEO	🟡 61	🟡 61	–
Bug prevention	🟢 100	🟢 100	–
Code style	🟢 100	🟢 100	–

👎 1 group regressed, 👍 2 audits improved, 👎 2 audits regressed, 14 audits changed without impacting score

🗃️ Groups

🔌 Plugin	🗃️ Group	⭐ Previous score	⭐ Current score	🔄 Score change
Lighthouse	Performance	🔴 48	🔴 48

19 other groups are unchanged.

🛡️ Audits

🔌 Plugin	🛡️ Audit	📏 Previous value	📏 Current value	🔄 Value change
Lighthouse	Largest Contentful Paint	🟨 3.6 s	🟨 3.8 s
Lighthouse	Speed Index	🟥 7.8 s	🟥 7.3 s
Lighthouse	First Contentful Paint	🟨 2.8 s	🟨 2.8 s
Lighthouse	Time to Interactive	🟥 17.7 s	🟥 18.3 s
Lighthouse	Avoids enormous network payloads	🟩 Total size was 1,821 KiB	🟩 Total size was 1,817 KiB
Lighthouse	Total Blocking Time	🟥 8,530 ms	🟥 11,020 ms
Lighthouse	Max Potential First Input Delay	🟥 3,200 ms	🟥 2,370 ms
Lighthouse	Eliminate render-blocking resources	🟥 Potential savings of 970 ms	🟥 Potential savings of 200 ms
Lighthouse	Metrics	🟩 100%	🟩 100%
Lighthouse	JavaScript execution time	🟥 11.4 s	🟥 11.9 s
Lighthouse	Uses efficient cache policy on static assets	🟨 28 resources found	🟨 28 resources found
Lighthouse	Reduce unused CSS	🟥 Potential savings of 82 KiB	🟥 Potential savings of 82 KiB
Lighthouse	Minimizes main-thread work	🟥 21.9 s	🟥 22.1 s
Lighthouse	Server Backend Latencies	🟩 80 ms	🟩 220 ms
Lighthouse	Initial server response time was short	🟩 Root document took 550 ms	🟩 Root document took 510 ms
Lighthouse	Network Round Trip Times	🟩 20 ms	🟩 30 ms
Lighthouse	Avoids an excessive DOM size	🟥 2,250 elements	🟥 2,248 elements
Code coverage	Line coverage	🟩 90.4 %	🟩 90.4 %

495 other audits are unchanged.

[matejchalk]

Did I miss something, or are there no e2e tests for the js-packages-plugin? Where could I write a test to show that the fix is working?

True, we don't have E2E tests for this plugin at present. We did attempt it, but making such tests stable was injustifiably complex (results change all the time, 4 package managers with different installations). In practice it's a lot simpler to fix post-release.