#24226 typescript-fetch: default to es6 support

default to ES6 support as ES5 support has been deprecated in TypeScript

FYI @TiFu (2017/07) @taxpon (2017/07) @sebastianhaas (2017/07) @kenisteward (2017/07) @Vrolijkx (2017/09) @macjohnny (2018/01) @topce (2018/10) @akehir (2019/07) @petejohansonxo (2019/11) @amakhrov (2020/02) @davidgamero (2022/03) @mkusaka (2022/04) @joscha (2024/10) @dennisameling (2026/02)

PR checklist

• Read the contribution guidelines.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in WSL)
  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

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Summary by cubic

Defaulted the typescript-fetch generator to ES2015+ and now produce dual builds (CommonJS + ESM) by default. This adds ESM output and package fields, and removes ES5-specific config.

• New Features

  • Always generate tsconfig.esm.json and build ESM to dist/esm via tsc && tsc -p tsconfig.esm.json.
  • package.json: add "module": "./dist/esm/index.js" and "sideEffects": false.
  • Remove legacy ES5 lib settings from tsconfig.
  • Update samples to reflect the new defaults.
  • Update tests to drop the ES5 path and expect ESM config by default.

• Migration

  • No changes needed for CommonJS consumers (main stays the same).
  • If you relied on ES5 targets, move to ES2015+ or add polyfills.
  • Remove any tooling that assumes a supportsES6-conditional output.