add package.json to module exports

[sebastiendavid]

PR description

Hello, I have this error with node@14.16.1, webpack@5.30.0 and jsonpath-plus@5.0.6:

Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: Package subpath './package.json' is not defined by "exports"

The pakage.json file is missing from exports and webpack is trying to require the file. I found the explanation on the yargs repository which had the same issue: yargs/yargs#1818

Checklist

• - Added tests
• - Ran npm test, ensuring linting passes
• - Adjust README documentation if relevant

[brettz9]

Thanks! Released in https://github.com/JSONPath-Plus/JSONPath/releases/tag/v5.0.7