v2.8.4 - fixes for older node versions

What's new

• baseline-browser-mapping is now a dependency of browserslist. The use of spread syntax and optional chaining in the source code caused build problems in older versions of Node.js (spread syntax in <8.3.0 and optional chaining in 14.0.0), so the build targets for baseline-browser-mapping have been changed to ES2017 to ensure compatibility.
• This release also changes the location of main in package.json to the CommonJS export, which should only be used in older versions of node. Any version of node using that supports ESM build should use the default location(s) in the exports property.

A big thank you to @BrightTan for identifying the issue in browserslist/browserslist#904 !

Full Changelog: v2.8.3...v2.8.4