Migrate to ESM

[int128]

git checkout -B migrate-esm

mv eslint.config.mjs eslint.config.js
cp ../typescript-action/jest.config.js .
cp ../typescript-action/tsconfig.json .
perl -i -p -e 'if (/^import/) { s/from '\''\.(.+)'\''/from '\''.$1.js'\''/g }' **/*.ts
perl -i -p -e 's/"dependencies": \{/"type": "module",\n  "dependencies": \{/' package.json
pnpm lint
pnpm test

git add .
git commit -m 'Migrate to ESM'
gh pr create -f --body '- https://github.com/int128/typescript-action/issues/782'