fix: use cross platform crypto for checksum verification in expo plugin

[Ayush4958]

Summary

• Replaced the shell based shasum command with Node's native crypto module.
• Retained the sync execution flow required by Expo config plugins by using fs.readFileSync combined with crypto.createHash('sha256').
• Formatted file according to project's Prettier config.

closes :- #322

Impact

• Cross platform support :- Windows developers can now successfully run expo prebuild to build for Android.
• Identical logic :- The SHA 256 hex digest perfectly matches the previous shasum -a 256 output format.

[changeset-bot]

⚠️ No Changeset found

Latest commit: e8b5228

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[Ayush4958]

@MrImmortal09
PR is ready for review

thanks ....