Language files do not work with ES modules in node

[sequba]

Description

Importing language files:

• seems to work in UMD module system
• seems to work in CommonJS although we should verify if the setup is optimal
• does not work in ESM in node
• does not work in ESM in React

Demo

https://codesandbox.io/p/devbox/test-hyperformula-with-nodejs-pgkwd8

Error messages

Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/workspaces/sandbox/node_modules/hyperformula/es/i18n/languages/frFR' imported from /workspaces/sandbox/index.js
Did you mean to import hyperformula/es/i18n/languages/frFR.js?

(node:328) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
(Use `node --trace-warnings ...` to show where the warning was created)
/workspaces/sandbox/node_modules/hyperformula/es/i18n/languages/frFR.js:417
export default dictionary;
^^^^^^

SyntaxError: Unexpected token 'export'

Notes

• Originally reported by @guenlm in Using language with script and CDN #1340
• Consulted with @budnix in https://handsoncode.slack.com/archives/D0300KBP0H2/p1701186053349819 (internal discussion)
• The fix might require a breaking change.

Related issues

• ESM module files in the published package should have .mjs file extension #1143
• Define the importable files through exports property in package.json #1144

[sequba]

Relevant discussion:

• Support .mjs output microsoft/TypeScript#18442
• Feature Request: allow change file extension of generated files from .ts  microsoft/TypeScript#49462
• https://www.sensedeep.com/blog/posts/2021/how-to-create-single-source-npm-module.html