Migrate package to ESM

[connor-baer]

Purpose

We're full-speed ahead on the migration to ES modules. This migration is inevitable anyway, and the ecosystem seems ready enough at this point (especially after #2053).

Sindre Sorhus has published an extremely helpful guide for pure ESM packages which I referenced throughout the migration.

Approach and changes

• Module resolution: ESM requires imports to use the full path to a file, including the file name (even for index files) and the file extension.
• package.json fields:
  • Added "type": "module" to the package:

    A package.json "type" value of "module" tells Node.js to interpret .js files within that package as using ES module syntax.

  • Switched to the "exports" field to configure the package entry point(s):

    The "exports" provides a modern alternative to "main" allowing multiple entry points to be defined, conditional entry resolution support between environments, and preventing any other entry points besides those defined in "exports".

  • Configured the "engines" field to require Node.js 18+, the first version of Node with full support for ES modules.

Definition of done

• Development completed
• Reviewers assigned
• Unit and integration tests
• Meets minimum browser support
• Meets accessibility requirements

[changeset-bot]

🦋 Changeset detected

Latest commit: dbdf233

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@sumup-oss/intl	Major

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.46%. Comparing base (e8f0005) to head (dbdf233).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #268   +/-   ##
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  Coverage   93.46%   93.46%           
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  Files          15       15           
  Lines         689      689           
  Branches       85       88    +3     
=======================================
  Hits          644      644           
  Misses         43       43           
  Partials        2        2           

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