feat(web-stack): add new i18n guidelines + ESLint + update and fixes

[ByScripts]

Description

• Add new i18n guidelines
• Remove nested keys: "foo": { "bar": "..." } ➡️ "foo.bar": "..." This makes code cleaner (and as a side-effect, it now allows to use foo + foo.bar keys)
• Lite/6 shared translations are no longer prefixed with core.
• Duplicated keys across translation files are no longer accepted. This will prevent accidental overwrite of missing common translations
• fr.json and en.json now required to contains the same keys
• Raw text is no longer accepted in template to prevent forgetting a translation Raw text is still accepted in dev-related files (stories, dev pages...)
• Remove useless alt on img
• Display of percentage now uses $n(value, 'percent')
• Removed legacy lite/src/i18n.ts
• Add missing translations
• Added visual indicator for missing translations while in dev env: 🌎❗⟨i-am-missing⟩

Checklist

• Commit
  • Title follows commit conventions
  • Reference the relevant issue (Fixes #007, See xoa-support#42, See https://...)
  • If bug fix, add Introduced by
• Changelog
  • If visible by XOA users, add changelog entry
  • Update "Packages to release" in CHANGELOG.unreleased.md
• PR
  • If UI changes, add screenshots
  • If not finished or not tested, open as Draft

[ByScripts]

@pdonias @MathieuRA Can you merge #7738 then this one? Thanks.

[pdonias]

I merged #7738, but now there are a few conflicts that need to be resolved before I can merge this one :)

[ByScripts]

@pdonias Done 👍🏻