Add localize-mixin sandbox demo

[bearfriend]

Adds a localize-mixin sandbox demo to interactively show how the mixin and messageformat itself works. It also includes generator templates and various message templates to demonstrate proper usage and formatting.

[bearfriend]

This was added here, unnecessarily because we reverted the related demo changes.

[dlockhart]

This is very cool! 😎

[github-actions]

Thanks for the PR! 🎉

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URL	https://live.d2l.dev/prs/BrightspaceUI/core/pr-3503/

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[dlockhart]

Really cool! As mentioned in standup, this might get even more visibility and use if it became part of our (currently sparse but hopefully better one day) localization documentation on the Daylight Site.

[dlockhart]

Maybe we should use a different analogy than number of legs for the basic & arguments templates? As it is, they might confuse people about how to actually do plurality. Maybe something like "The octopus lives in the ocean" and "The {animalType} lives {animalHome}"? 🤷

[bearfriend]

Yep, it confused me during my own demo

[bearfriend]

Really cool! As mentioned in standup, this might get even more visibility and use if it became part of our (currently sparse but hopefully better one day) localization documentation on the Daylight Site.

I'm going to look into this now