Add module to package.json

[denisx]

What issue does this pull request resolve?

To emulate esm build, you need couple thing at package.json: module and sideeffects

What changes did you make?

Bundlers will cut unused code better then now. Goog for named imports.

[denisx]

@eventualbuddha @Delapouite hello here! )

[jasoniangreen]

Thanks for your contribution @denisx. This change seems to be correct to me, just give me some time to double check.

[michaelgiraldo]

@jasoniangreen Thanks again for maintaining Ajv! With ESM support, this PR removes the need for interop shims and enables much cleaner imports, especially as projects move toward Node’s ESM defaults. Excited to see it land.