fix: correct package entry paths

[luuhongyii]

Summary

• point the package main entry at plugin/build/withIterable.js
• point the package types entry at plugin/build/withIterable.d.ts

Why

The published @iterable/expo-plugin@1.0.2 package declares main: "build/withIterable.js" and types: "build/withIterable.d.ts", but those files are not present in the npm tarball. The plugin build output is published under plugin/build/, which is also the path used by app.plugin.js.

Validation

• checked the published npm tarball: package/build/withIterable.js and .d.ts are absent, while package/plugin/build/withIterable.js and .d.ts are present
• corepack yarn install --immutable
• corepack yarn tsc -p plugin/tsconfig.json --pretty false
• npm pack --dry-run --ignore-scripts --json confirms the updated main and types files are included
• git diff --check