Internationalize Node app template

WHY are these changes introduced?

Translating apps is technically challenging, time-consuming, and costly. Despite the high demand for localized apps internationally, only a small fraction of apps offered in the Shopify App Store are translated.

None of Shopify's app templates are localized, meaning that the full burden of responsibility is on the developer to research and implement an i18n framework for their app. It’s also more likely to be an afterthought until the developer decides to expand internationally, at which point the effort to externalize all the app's strings is much higher.

By localizing the default Node app template, we reduce the toil for developers, and set them up to localize their apps from the start.

WHAT is this pull request doing?

Update the front end app template to be internationalized (more details in this pull request)
Update the README to list the dependencies introduced and link to relevant developer resources

English:

French:

German:

How to test

npm init @shopify/app@latest -- --template https://github.com/shopify/shopify-app-template-node#add-i18next
npm run build
npm run dev

Checklist

Note: once this PR is merged, it becomes a new release for this template.

[x] Use the front end template from main once this PR is merged
[ ] ~I have added/updated tests for this change~
[x] I have made changes to the README.md file and other related documentation, if applicable

Shopify / shopify-app-template-node