Update postinstall script to reference component's package.json with an absolute path

[chrisfalaska]

Please describe the bug

When using postInstall.mjs as part of auro-library, the script attempts to reference a relative package.json:

const pjson = require('../package.json');

If a component such as auro-input is referencing postInatll.mjs from auro-library, the install fails since it cannot find a relative package.json inside auro-library node_modules:

Error: Cannot find module '../package.json'

Reproducing the error

• From your respective component's package.json (for example: auro-input), reference the postInstall.mjs script from auro-library:

"postinstall": "node ./node_modules/@aurodesignsystem/auro-library/scripts/build/postinstall.mjs",

• Run npm i

• Observe build error.

Expected behavior

The postInstall script should run from node_modules and reference the consuming component's package.json

What browsers are you seeing the problem on?

No response

Additional context

Part of the monorepo work in auro-form: AlaskaAirlines/auro-formkit#1

Exit criteria

No response