This commit fixes the broken stackblitz example of i18n. Closes #41838. PR Close #42001
The Stackblitz and zip-file include `doc-files` unnecssarily and are missing the locale files. This commit updates the `stackblitz.json` to fix this. PR Close #37947
Rewrite headings to focus on tasks and separate reference info and best practices from tasks. Add missing steps or procedures, and links to important information. Make the example open in StackBlitz. See i18n Documentation Plan at https://docs.google.com/document/d/1aV2TKsIqry7JnNiHEfhmheu5rNAbNl1IRYVhYErc7Ks/edit?usp=sharing PR Close #36924