Internationalization of Lighthouse (Phase 2)

[paulirish]

Picking up after #5719

Known work

• bring back https://github.com/GoogleChrome/lighthouse/pull/5726/files#diff-4bcfedf0736e1cd08b26fe659537ad90 to avoid A11y i18n #7010. i18n: enable local debug locale, en-XL #9192
• figure out Node's ICU support on Travis/Appveyor (Number.toLocaleString appears to always use 'en-US' - Travis failure)
  • presumably the node install is system-icu or small-icu
  • can we resolve with an NVM flag or travis config?
  • or better polyfilling. Fix in core(i18n): improve Intl polyfill and use it in Util #9584
• revamp i18n.lookupLocale and locale list to better canonical lookups
  • Intl.NumberFormat.supportedLocalesOf(['no', 'tl']) === [], so even though we support those locales in translations they get the wrong (?) number formatting, plurals, etc by falling back to a default locale (en, probably). Why do these in particular fail but all the others work?
• text baked into the report HTML
  • export dropdown i18n(report): runtime settings and tools #9166
  • header metadata
  • footer runtime settings i18n(report): runtime settings and tools #9166
  • Number.toLocaleString all numbers in report
    • scorescale!
  • aria labels
• a11y manual audits
• Translating strings from gatherers (error messages, etc)

finish complete l10n of lighthouse

• localize error messages. Localize the error messages #6441
• localize remaining categories
  • seo
  • best-practices i18n: localize audits in best-practices #9092
  • pwa i18n: pwa #9105
• localize stack packs?
• move pwa audits to audits/pwa folder
• move best-practices audits to audits/best-practices
• RTL layout @paulirish
• lang attribute report(i18n): set lang attribute according to locale #5805
• include locale json files in build
• warnings
• Date/Time Locales Report generated time is always in en-US #1703
• PSI swap langs? 😮 this guy wants it
• proto refactor i18n section. @past-shane you really messed this one up.
• Placeholder syntax i18n: placeholders #9114 to prevent Translation messing up linked docs in dom-size #9000
  • fix i18n guffaws A Collection of i18n Markdown Guffaws 😭😭😭 #9197
• es-419
• viewer locale swap?
• read locale info from system? e.g. Report generated time is always in en-US #1703
• i18n concat'd lists, like this

ship it

• [ ] ship l10n'd lighthouse to extension
• ship l10n'd lighthouse in devtools audits panel
• enable web.dev to use full l10n'd lhrs if they want

Plz add anything else here

[exterkamp]

Added some things that are todo