Add ./package.json as an export entry

[ahmedelgabri]

This will avoid breaking older tools that try to read package.json files from packages using package name instead of absolute path.

Because when exports is set, accessing files that's not specified in the exports property is not allowed by node and it will throw a ERR_PACKAGE_PATH_NOT_EXPORTED error (rightly so).

This easily reproducible in the node repl.

This will throw

require.resolve('immer/package.json')

This will not throw

require.resolve('./node_modules/immer/package.json')

Something similar has been mentioned in this great article https://blog.isquaredsoftware.com/2023/08/esm-modernization-lessons/#issue-history by @markerikson (sorry for the ping, feel free to ignore) when he worked on modernizing @reduxjs/toolkit (which depends on immer and this is how I found the issue)

Similar issues in the wild on GitHub for Package subpath './package.json' is not defined by "exports" https://github.com/search?q=%22Package+subpath+%27.%2Fpackage.json%27+is+not+defined+by+%22exports%22%22&type=issues

[mweststrate]

Thanks! Let's hope this doesn't explode something for someone somewhere. Given that it touches package config, it probably will🥹

[coveralls]

Pull Request Test Coverage Report for Build 8356888414

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 99.793%

---

Totals
Change from base Build 8240372216:	0.0%
Covered Lines:	647
Relevant Lines:	648

---

💛 - Coveralls

[github-actions]

🎉 This PR is included in version 10.1.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀